PYONGYANG • To fly into North Korea on an old Russian aircraft is to step into an alternative universe, one in which "the Supreme Leader" defeats craven US imperialists, in which triplets are taken from parents to be raised by the state, in which nuclear war is imminent but survivable - and in which there is zero sympathy for US detainees like the late Otto Warmbier.

Mr Warmbier was the University of Virginia student who was arrested for stealing a poster, then sentenced to 15 years of hard labour and eventually returned to the United States in a vegetative state.

"He broke the law in our country," said Foreign Ministry official Ri Yong Pil, adding that Mr Warmbier was returned (a week before his death) as a "humanitarian" act.

Another official, Mr Choe Kang Il, insisted that North Korea had provided excellent care and spent "all the money for nursing" him.

Something in me snapped. I asked how North Koreans could possibly boast about their spending on a young man when he was in a coma only because of them. Mr Choe replied just as hotly that Mr Warmbier had not been mistreated and was in fine condition when he was sent back home.

"The US administration, or some people with a certain intention, let him die," Mr Choe said. "This must be intended to foster and spread anti-communist hatred within America."

Officials offered no apology and gave no ground, reflecting a hard line towards the US that I found everywhere on this visit; Mr Choe derided President Donald Trump as "a crazy man", "a thug" and "a pathetic man with a big mouth".

I've been covering North Korea on and off since the 1980s, and this five-day trip has left me more alarmed than ever about the risks of a catastrophic confrontation.

I was given a visa to North Korea, as were three other New York Times journalists. The US State Department promptly gave us an exemption from the travel ban to North Korea and issued special passports good for a single trip here.

Far more than when I previously visited, North Korea is galvanising its people to expect a nuclear war with the US.

High school students march in the streets in military uniform daily to denounce America. Posters and billboards along public roads show missiles destroying the US Capitol and shredding the American flag.

In fact, images of missiles are all over the place - in a kindergarten playground, at a dolphin show, on state television. This military mobilisation is accompanied by the ubiquitous assumption that North Korea could not only survive a nuclear conflict, but also win it.

"If we have to go to war, we won't hesitate to totally destroy the United States," explained 38-year-old teacher Mun Hyok Myong, visiting an amusement park.

Mr Ryang Song Chol, a 41-year-old factory worker, looked surprised when I asked if his country could survive a war with America. "We would certainly win," he said.

'WIMPISH' DIPLOMATS

These interviews were conducted in the presence of two Foreign Ministry officials, but even if they weren't, there is no chance that ordinary people would speak freely to a foreign reporter. This is perhaps the most tightly controlled country in the world, so such quotes should be seen as reflecting a government script - in this case, a disturbingly jingoistic one.

On past trips (my last was in 2005), we journalists stayed at hotels in Pyongyang and were free to walk around on our own, but this time, the Foreign Ministry housed us at its own guarded Kobangsan Guest House east of the capital. At first I thought this was simply to restrict us, but increasingly I saw signs of something more interesting and menacing: The Foreign Ministry was also protecting us from hardliners in the military or in the security services.

"Someone might hear you are from America" and there could be trouble, one official explained.

Hardliners seem to have gained greater power this year, especially after Mr Trump's threat to "totally destroy" North Korea, and we were told that military officers sometimes mock their own country's diplomats for being wimpish "American cronies".

Foreign Ministry officials escorted us each time we left the compound, probably both to keep us out of mischief and to protect us from the security agencies.

All this has been a little discomfiting. The upshot is that I have felt more constraint than on past visits to North Korea, and considerably more tension. Before, I had been able to see senior generals, but this time, the military flatly refused to consider my interview requests.

The security forces also refused my request to meet the three Americans still being held, one for two years now, without consular access.

A basic problem is that hardliners seem ascendant in both Washington and Pyongyang.

In Washington, Secretary of State Rex Tillerson is advocating a diplomatic resolution to conflict with North Korea - but Mr Trump undercut him on Twitter and said Mr Tillerson was "wasting his time".

Mr Trump's policy towards North Korea is founded on the false assumptions that its Supreme Leader, Mr Kim Jong Un, will give up his nuclear weapons, that China can save the day and that military options are real.

In Pyongyang, North Korea's capital, which is full of wide streets and monumental buildings, officials also express little interest in the kind of tough compromises necessary to resolve the crisis.

"The situation on the Korean peninsula is on the eve of the breakout of nuclear war," Mr Choe, the Foreign Ministry official, told me. "We can survive" such a war, he added, and he and other officials said it was not the right time for talks with the US.

The North Koreans insist that the Americans make the first move and drop their sanctions and "hostile attitude" - which won't happen. And the US is equally unrealistic in insisting that North Korea give up its entire nuclear programme.

I told Mr Choe that my visit gave me a sense of deja vu, reminding me of a trip to Saddam Hussein's Iraq on the eve of the US invasion. The difference is that a war here would be not just a regional disaster but a nuclear cataclysm.

Mr Choe was unimpressed by my warning. He said Iraq and Libya had made the mistake of giving up their nuclear programmes; in each case, America then ousted the regime. He added that the lesson was obvious, so North Korea will never negotiate away its nuclear warheads.

CHANGING NORTH KOREA

Still, for all the shadow of possible war, there are some positive changes in North Korea. The famine is over (although malnutrition still leaves one in four children stunted), the economy has developed and government officials are far more open and savvy than those of a generation ago.

Officials used to deny that there was ever any crime in North Korea - but now they freely concede that this country has thieves, that young women sometimes become pregnant before marriage, that inevitably there's a measure of corruption. (They do deny that North Korea has any gay people.)

North Korea is no longer hermetically sealed, and South Korean pop music and soap operas are smuggled in on flash drives and DVDs from China, (watching them is a serious criminal offence). There is also an intranet - a rigidly controlled domestic version of the Internet - and students learn English from about the third grade.

At the best schools, like Pyongyang No. 1 Secondary School, the students are extraordinarily bright, and they conversed with us in fluent English, with far more sophistication than on my first visit to the same school in 1989.

Yet this is still North Korea. I asked these kids if they had ever heard of Beyonce or the Beatles; none had. I asked if they had heard of Facebook. One had, because computer software sometimes referred to it, but he didn't know what it was.

Radio or TV sets that might receive foreign broadcasts are illegal, and there is no access to the Internet except for foreigners and senior officials.

When I arrived at the airport, my luggage was closely searched for pernicious publications, and even my phone was examined.

"Who's this person," the Customs official asked suspiciously when she saw an Asian woman appear frequently in my photos.

"My wife," I explained.

"Oh," she said, deflated. "She's pretty."

Each home or village has a speaker, a link from Big Brother, that drums in propaganda every morning. Religion and civil society are not allowed.

Government controls frayed during the terrible famine of the 1990s, when perhaps 10 per cent of the population died, but the controls have returned with the economic recovery.

This is the most totalitarian state in the history of the world, because it has computers, closed-circuit cameras, mobile phones and other monitoring technologies that Stalin or Mao Zedong could only have dreamed of.

North Korea is also at times just weird. Triplets are taken from their parents and raised by the state because they are deemed auspicious.

The personality cult is unyielding - all adults wear pins of "the Great Leader", Kim Il Sung, who died in 1994, or his son, "the Dear Leader", Kim Jong Il, who died in 2011, and their portraits are in every home, every factory, every classroom.

Every year, people die trying to rescue the Kim portraits from house fires (whether because of genuine loyalty or to win credit with the authorities), and now this Confucian-style reverence is directed to Mr Kim Jong Un, 33, the scion of the dynasty. His name means "just and merciful", and the state media is worshipful about his "brilliant intelligence, military acumen, matchless courage and outstanding art of command", as one publication puts it.

Somehow, for all the official hostility, North Koreans tend to be friendly to individual Americans. At the new science and technology tower in Pyongyang, I met a 13-year-old boy, Paek Sin Hyok, who daily participates in military parades at his middle school to mobilise for war. It was his first time meeting Americans, and he said his heart was thumping.

I asked him about the common North Korean expression that "just as a wolf cannot become a lamb, so an American imperialist can never change his aggressive nature". "What about us?" I asked him. "Are we wolves? Or lambs?" He struggled with how to answer that politely. "Half and half," he said.

With this mutual distrust, it's easy to see how things might go wrong. I suspect North Korea is rational and cares about self-preservation, and I don't believe it would fire off a nuclear missile at Guam or Los Angeles just for the thrill.

But a dogfight between a North Korean plane and a US jet could cause a crisis that escalates.

Or Mr Trump could order an airstrike on a North Korean missile during fuelling on the launchpad - and that, every North Korean official said, would lead to war.

Both sides are on a hair trigger.

That's why in war games, conflicts quickly escalate - and why the US military estimated back in 1994 that another Korean war would cause one million casualties and a trillion dollars in damage.

Today, with the possibility of an exchange of nuclear weapons, the toll could be far greater: One recent study suggested that if North Korea detonated nuclear weapons over Tokyo and Seoul, deaths in those two cities could exceed two million.

My sense is that both sides are fearful of appearing weak and are trying to intimidate the other with military bluster, but that each would prefer a peaceful resolution - yet doesn't know how to get there politically.

So how do we get out of this mess?

First, Mr Trump should stop personalising and escalating the conflict.

Second, we need talks without conditions, if only talks about talks: I'd suggest a secret visit to Pyongyang by a senior administration official, as well as discussions with North Korea's ambassador to the United Nations.

Third, human rights have to be part of the agenda, backed by the threat of suspending North Korea's credentials at the UN.

Fourth, we should support organisations that smuggle information on USB drives into North Korea; this would be cheap and might contribute to change in the long term.

Fifth, increase cyber warfare, which the US has already used effectively against North Korea.

Sixth, enforce tighter sanctions, but only if harnessed to a plausible outcome.

Ultimately, the best hope that is realistic may be a variant of what's called a "freeze for a freeze", with North Korea halting its nuclear and missile tests in exchange for a reduction in sanctions and in military exercises between the US and South Korea - as an interim step, preserving the long-term goal of denuclearisation.

Unfortunately, both sides resist this approach; I was disappointed in the lack of North Korean interest.

So if we can't work out a "freeze for a freeze", realistically the next best option is to settle into long-term mutual deterrence. But that would be risky, not least because we have a US president and a North Korean leader who both seem impetuous, overconfident and temperamentally inclined to escalate any dispute - and the US mainland increasingly will be in the cross hairs of North Korean nuclear warheads.

I leave North Korea with the same sense of foreboding that I felt after leaving Saddam's Iraq in 2002. War is preventable, but I'm not sure it will be prevented.

NYTIMES