WASHINGTON • North Korea's test-firing of a missile apparently capable of reaching Alaska underlines the shrinking options for US President Donald Trump to halt Pyongyang's nuclear drive after losing faith in China's mediation efforts.
Shortly before his January inauguration as president, Mr Trump said he would never let North Korea develop a nuclear weapon that would put parts of the United States in range, declaring on Twitter: "It won't happen!"
But after Washington confirmed that North Korea had successfully tested an intercontinental ballistic missile (ICBM), experts say the US may have to accept that that red line is close to being crossed if the missile system can be developed to carry a nuclear warhead.
Dr Jeffrey Lewis, an expert in nuclear non-proliferation, said: "The window for negotiating denuclearisation is closed. The big point is that we have to accept North Korea with a nuclear-armed ICBM."
In the aftermath of Tuesday's ICBM test, Mr Trump again took to Twitter to berate the North's leader, Mr Kim Jong Un, and press China to "put a heavy move on North Korea and end this nonsense once and for all".
But there are growing signs that he has already effectively given up on Beijing's capability of reining in the Pyongyang regime, declaring last month that Chinese efforts had not worked out.
The Trump administration's hardening stance was also illustrated last Thursday when it imposed sanctions on a Chinese bank linked to North Korea - drawing an angry response from Beijing.
NEW STRATEGY NEEDED
Denuclearisation is untenable. US policy failed. The best we can hope for now is to sustainably deter, contain, constrain and reform the regime over the long term.
MR ADAM MOUNT, a senior fellow at the Centre for American Progress for Nuclear and Defence policy, on how North Korea has crossed the line by successfully test-firing an ICBM.
In a weekend phone call with Chinese President Xi Jinping, Mr Trump reportedly told Mr Xi that the US was prepared to act on its own in pressuring North Korea, according to the New York Times.
As well as leaning on China, Mr Trump had also been seeing if he could work with South Korea's new president, Mr Moon Jae In, inviting him to the White House last week.
Mr Adam Mount, a senior fellow at the Centre for American Progress for Nuclear and Defence policy, said that international pressure and diplomacy were of limited use now that Pyongyang was so far down the line. "It is now illogical to apply pressure to prevent the threshold from being crossed. It has been crossed. Denuclearisation is untenable," he said.
"US policy failed. The best we can hope for now is to sustainably deter, contain, constrain and reform the regime over the long term."
In the short term, the Pentagon is studying its options for military action, although the US and South Korea quickly made a show of force following the ICBM test, firing missiles off the coast of the Korean peninsula in what Washington called a display of "precision fire capability". But US military chiefs have made clear that they see enormous risks in a confrontation with the North.
Speaking in May, US Secretary of Defence Jim Mattis said that any war with North Korea would be on a scale similar to the devastating Korean War in the 1950s.
"The North Korean regime has hundreds of artillery cannon and rocket launchers within range of one of the most densely populated cities on earth, which is the capital of South Korea," he told CBS News.
"The bottom line is, it would be a catastrophic war if this turns into a combat, if we are not able to resolve this situation through diplomatic means."
Dr Lewis, who is a researcher at the California-based Middlebury Institute for International Studies, said the Trump administration's focus now should be on dissuading North Korea from firing anything in earnest.
"We should consider ways to reduce tension while strengthening deterrence," he said. "Ballistic missile defence might be part of the deterrence."