WASHINGTON • President Donald Trump has said he wants to ensure that the United States' nuclear arsenal is at the "top of the pack", saying the country has fallen behind in its weapons capacity.

In a Reuters interview on Thursday, Mr Trump also said China could solve the national security challenge posed by North Korea "very easily if they want to", ratcheting up pressure on Beijing to exert more influence to rein in Pyongyang's increasingly bellicose actions.

Mr Trump also expressed support for the European Union as a governing body, saying "I'm totally in favour of it", and for the first time as President expressed a preference for a two-state solution to the Israeli-Palestinian conflict, but said he would be satisfied with whatever makes the two sides happy.

He also predicted that his efforts to pressure allies in the North Atlantic Treaty Organisation to pay more for their own defence and ease the burden on the US Budget would reap dividends. "They owe a lot of money," he said.

In his first comments about the US nuclear arsenal since taking office on Jan 20, Mr Trump was asked about a December tweet in which he said the US must greatly strengthen and expand its nuclear capacity "until such time as the world comes to its senses regarding nukes".

He said in the interview that he would like to see a world with no nuclear weapons but expressed concern that the US has "fallen behind on nuclear weapon capacity".

"I am the first one that would like to see... nobody have nukes, but we're never going to fall behind any country even if it's a friendly country, we're never going to fall behind on nuclear power.

"It would be wonderful, a dream would be that no country would have nukes, but if countries are going to have nukes, we're going to be at the top of the pack," he said.

Russia has 7,000 warheads and the US has 6,800, said the Ploughshares Fund, an anti-nuclear group.

And Mr Daryl Kimball, executive director of the Arms Control Association, an independent non-profit group, said: "Russia and the United States have far more weapons than is necessary to deter nuclear attack by the other or by another nuclear- armed country."

The new strategic arms limitation treaty between the US and Russia, known as New Start, requires that by Feb 5 next year, both countries must limit their arsenals of strategic nuclear weapons to equal levels for 10 years.

The treaty permits both nations to have no more than 800 deployed and non-deployed land-based intercontinental and submarine- launched ballistic missile launchers and heavy bombers equipped to carry nuclear weapons, and has equal limits on other nuclear weapons.

Analysts have questioned whether Mr Trump wants to abrogate New Start or would begin deploying other warheads.

In the interview, Mr Trump called New Start "a one-sided deal", saying it is "just another bad deal that the country made, whether it's Start, whether it's the Iran deal".

The US is in the midst of a US$1 trillion (S$1.4 trillion), 30-year modernisation of its ageing ballistic missile submarines, bombers and land-based missiles.

Mr Trump expressed concern about North Korea's ballistic missile tests and said that accelerating a missile defence system for US allies Japan and South Korea was among many options available.

"There are talks of a lot more than that," he said when asked about the missile defence system. "We'll see what happens. But it's a very dangerous situation, and China can end it very quickly in my opinion."

China has made clear that it opposes North Korea's nuclear and missile programmes and has repeatedly called for denuclearisation of the Korean peninsula and a return to negotiations between Pyongyang and world powers.

REUTERS