Donald Trump's bellicose rhetoric aimed at North Korea has pushed the US and the communist dictatorship to the brink of nuclear war, according to the North Korea's foreign minister.

"By his belligerent and insane statement at the United Nations, Trump, so to say, lit the fuse of war against us," Ri Yong Ho told Russia's state-run news agency TASS.

"We need to settle the final score, only with a hail of fire, not words."

During his maiden speech to the UN, Trump mocked Kim Jong-un, dubbing him "Rocket Man" and warning that the US may be forced to "totally destroy" the rogue nation, the New York Post reported.

Advertisement

"If the righteous many do not confront the wicked few, then evil will triumph," Trump said. "Rocket Man is on a suicide mission."

Ri's threats came a day after a pair of US bombers for the first time conducted manoeuvres over the Korean peninsula with the South Korean air force, and followed stepped-up sabre-rattling by the president on Twitter.

Trump has repeatedly suggested military action was the only solution to the North's belligerence and growing nuclear weapons and missile program.

"Presidents and their administrations have been talking to North Korea for 25 years, agreements made and massive amounts of money paid hasn't worked, agreements violated before the ink was dry, makings fools of US negotiators. Sorry, but only one thing will work!" he tweeted on Saturday.

"Our country has been unsuccessfully dealing with North Korea for 25 years, giving billions of dollars & getting nothing. Policy didn't work!" he added in another tweet two days later.

North Korea has launched two missiles over Japan and conducted its sixth nuclear test in recent weeks as it advances quickly toward its goal of developing a nuclear-tipped missile capable of hitting the US mainland.

The two Air Force B-1B bombers were joined by two F-15K fighters from the South Korean military after leaving their base in Guam, South Korea's Joint Chiefs of Staff said.

After entering South Korean airspace, the two bombers carried out air-to-ground missile drills in waters off the east coast of South Korea, then flew over the South to waters near China to repeat the drill, the military said.

The foreign minister told TASS that his country was getting close to achieving its goal of assembling a nuclear arsenal.

"We have nearly achieved the final point on the way to our ultimate goal, to achieving a real balance of force with the United States. Our nuclear weapons will never be a subject matter of negotiations as long as the United States' policy of pressure on the DPRK has not been uprooted once and for all," he said.

Arsenal increase

Meanwhile Trump reportedly pushed for a tenfold increase in the country's nuclear arsenal.

The President told a meeting of his national security advisers in July that he wanted to boost the country's weapon stocks, NBC News reported.

However the president denied the report, saying he wants the repository modernised and in "tiptop shape".

In remarks in the Oval Office yesterday Trump denounced the NBC report and said such a big increase was "totally unnecessary".

"I want to have absolutely, perfectly maintained - which we are in the process of doing - nuclear force," he said.

"But when they said I want 10 times what we have right now, it's totally unnecessary, believe me, because I know what we have right now. We won't need an increase but I want modernisation and I want total rehabilitation. It's got to be in tiptop shape."

By saying he wants to modernise the nuclear force, Trump is referring to moving ahead with a plan he inherited from the Obama administration to develop, build and field new submarines armed with nuclear missiles; new nuclear-capable bomber aircraft and a new fleet of land-based intercontinental ballistic missiles.

North Korea's Foreign Minister Ri Yong-ho accused Mr Trump of 'setting a fuse of war' with his September speech at the United Nations. Photo / AP
North Korea's Foreign Minister Ri Yong-ho accused Mr Trump of 'setting a fuse of war' with his September speech at the United Nations. Photo / AP

These would replace existing weapons that are considered outdated. Also in the works is an upgrade of communications systems that enable the president and the Pentagon to command and control the weapons.

Shortly after Trump spoke, Defense Secretary Jim Mattis issued a two-sentence statement saying the news report was false and irresponsible.

"Recent reports that the president called for an increase in the U.S. nuclear arsenal are absolutely false," Mattis statement said.

Trump's previous comments about nuclear weapons have caused confusion and concern in some quarters.

Last December, for example, he suggested he favoured expanding the nuclear arsenal.

"The United States must greatly strengthen and expand its nuclear capability until such time as the world comes to its senses regarding nukes," he said then.

The US is party to a 2010 arms control deal with Russia that limits each nation to 1550 deployed strategic nuclear warheads.

As of September 1, the US had 1393 and Russia had 1561. They agreed to reach the 1550 level or lower by February 2018.

The US currently has about 4000 nuclear warheads earmarked for use in its military stockpile, according to the Federation of American Scientists' figures cited by Reuters.