AMERICA’S chief diplomat has claimed North Korea is “begging for war” and has urged the United Nations Security Council to impose the strongest possible sanctions on the rogue state.

The stark intervention from Nikki Haley, the US ambassador to the UN, came as Pyongyang was said to be preparing more missile launches following its underground test at the weekend of a bomb three times the size of that dropped on Hiroshima in 1945.

Donald Trump has spoken to Moon Jae-in, the South Korean President, saying the North's latest nuclear test was an “unprecedented” provocation.

Seoul says Pyongyang is preparing to launch another ballistic missile and believes it now has the capacity to put a nuclear warhead on it.

In response to North Korea’s latest test, the South undertook live-fire drills off its eastern coast meant to simulate an attack on the North's main test site.

During an emergency meeting of the UNSC in New York, the second in a week, Ms Haley declared: “Enough is enough. The time for half-measures in the Security Council is over. The time has come to exhaust all of our diplomatic means before it’s too late.”

She noted: "War is never something the United States wants. We don't want it now but our country's patience is not unlimited."

Ms Haley spoke after the US President warned that America could consider stopping all trade with any nation doing business with North Korea.

"The United States will look at every country that does business with North Korea as a country that is giving aid to their reckless and dangerous nuclear intentions," explained Ms Haley.

In a telephone conversation, Germany’s Angela Merkel and Mr Trump agreed on the need for stricter sanctions.

Last month, the UNSC voted unanimously to ban North Korean exports and limit investments in the country.

Matthew Rycroft, the UK ambassador to the UN, described the current situation as "disturbing and unprecedented" but stressed the UNSC sanctions were "having an effect" on the communist regime.

He called on the UNSC to condemn the latest test and said: "We continue to wish for a peaceful way forward: dialogue will always be our end goal but returning to dialogue without a serious sign of intent from Pyongyang would be a set up to failure.

"North Korea must change course to allow a return to dialogue. Were they to do so the opportunity exists to end this crisis,” declared Mr Rycroft.

He went on: "Until that moment we must stay the course on sanctions and continue, as the Secretary General has called for, to present a united front."

He restated his calls for a new UNSC resolution and said in light of the latest test: "We must increase the pace of implementation of existing sanctions and work rapidly towards the adoption of a new and effective resolution."