America’s top diplomat has warned that North Korea is “begging for war” and urged the UN security council to impose the toughest sanctions possible on the isolated dictatorship.

The blunt statement by Nikki Haley, the US ambassador to the United Nations, came as Donald Trump spoke with South Korean president Moon Jae-in and agreed that the North’s latest nuclear test was an “unprecedented” provocation.

North Korea carried out its sixth and by far most powerful nuclear test on Sunday. The underground blast triggered a magnitude 6.3 tremor and was more powerful than the bombs dropped by the US on Hiroshima and Nagasaki during the second world war.

“Enough is enough,” said Haley, noting that an approach of incremental sanctions since 2006 had not worked. “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.”

Nuclear powers understand their responsibilities, she added, and Kim Jong-un has shown no such understanding. “His abusive use of missiles and his nuclear threats show that he is begging for war. War is never something the United States wants. We don’t want it now. But our country’s patience is not unlimited. We will defend our allies and our territory.”

Haley said her country would circulate a resolution this week with the aim of getting it approved next Monday and, in a thinly veiled jab at China, said the US would target countries trading with Pyongyang, a prospect also raised by Trump on Sunday.

“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,” she said. “The stakes could not be higher.”

She added: “Only the strongest sanctions will enable us to resolve this problem through diplomacy. We have kicked the can down the road long enough. There is no more road left.”

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Trump and Moon spoke for around 40 minutes by phone on Monday, according to South Korea’s presidential office. Trump reaffirmed an “ironclad” commitment to South Korea’s defence, it said, and the two countries agreed to seek stronger UN sanctions against the North.

The leaders also agreed to remove a limit on the payload of South Korean missiles in response to the North’s nuclear test, which they saw as a grave provocation that was “unprecedented”.

In the wake of the North Korean test on Sunday, Trump accused South Korea of “appeasement”, adding to tensions raised by his possible withdrawal from a free trade agreement with Seoul.

The Kremlin said Moon had also spoken with Russian president Vladimir Putin. Spokesman Dmitry Peskov told reporters: “It is very easy to say the word ‘war’ for countries outside the region, but those in the region need to be smarter and more balanced.”

The US, UK, France, Japan and South Korea requested Monday’s urgent UN security council meeting after North Korea detonated what it described as a hydrogen bomb designed for a long-range missile. North Korea also tested two intercontinental ballistic missiles in July that could fly about 6,200 miles, putting many parts of the US mainland within range and prompting Trump to threaten “fire and fury” in response.

Facebook Twitter Pinterest In Tokyo, people walk past a news broadcast showing Japanese prime minister Shinzo Abe and US president Donald Trump following North Korea’s nuclear test. Photograph: Shizuo Kambayashi/AP

The security council has imposed seven sets of sanctions on North Korea since it first tested a nuclear device in 2006, but Pyongyang has repeatedly found ways to circumvent the measures. The most recent resolutions, however, have significantly toughened the sanctions, targeting key exports sectors such as coal that are a source of hard currency for Kim’s regime.

Addressing the council, Haley rejected as “insulting” a Chinese proposal for a freeze on North Korea’s nuclear and missile programmes in exchange for a suspension of US-South Korean annual military drills. “When a rogue regime has a nuclear weapon and an ICBM [intercontinental ballistic missile] pointed at you, you do not take steps to lower your guard. No one would do that. We certainly won’t.”

But Liu Jieyi, the Chinese ambassador to the UN, said: “The situation on the peninsula is deteriorating constantly as we speak, falling into a vicious circle. The peninsula issue must be resolved peacefully. China will never allow chaos and war on the peninsula.”

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Russia backs China’s proposal for a freeze on North Korea’s nuclear and missile tests in exchange for a suspension of US-South Korea military drills. Russian ambassador Vassily Nebenzia told reporters after Monday’s meeting: “Resolutions aimed solely at sanctioning North Korea have not worked well before.”

Reuters reported that diplomats have said the security council could now consider banning North Korean textile exports and its national airline, stopping supplies of oil to the government and military, preventing North Koreans from working abroad and adding top officials to a blacklist to subject them to an asset freeze and travel ban.

Matthew Rycroft, the UK ambassador to the UN, described the situation as “disturbing and unprecedented”, but said it was “clear” sanctions applied by the Security Council on North Korea were “having an effect”.

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

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French ambassador Francois Delattre said France was calling for the adoption of new UN sanctions, swift implementation of existing ones and new separate sanctions by the European Union.

Japanese ambassador Koro Bessho told reporters ahead of the council meeting: “We cannot waste any more time. And in order to do that, we need North Korea to feel the pressure, but if they go down this road there will be consequences.”

South Korea’s defence ministry warned on Monday that Pyongyang may be preparing another missile launch after two tests in July of ICBMs that apparently brought the US mainland into range.

Jang Kyoung-soo, acting deputy minister of national defense policy, told a parliamentary hearing on Monday: “We have continued to see signs of possibly more ballistic missile launches. We also forecast North Korea could fire an intercontinental ballistic missile.”

South Korea said its air force and army conducted exercises involving long-range air-to-surface and ballistic missiles on Monday. In addition to the drill, South Korea will cooperate with the United States and seek to deploy “strategic assets like aircraft carriers and strategic bombers”, Jang said.

US defence Secretary James Mattis has warned of “a massive military response” to any threat from North Korea against the US or its allies.