Defying pressure from new United Nations sanctions, North Korea threatened to use nuclear weapons against the US if militarily provoked and said it would “under no circumstances” negotiate on its nuclear and missile weapons programmes.

North Korean Foreign Minister Ri Yong Ho on Monday delivered the strongly worded statement to reporters on the sidelines of an Asian regional security conference hours after US Secretary of State Rex Tillerson vowed to implement the stiffest sanctions yet imposed on the Pyongyang regime.

Washington is seeking to build support in its campaign to pressure North Korea to give up its nuclear program after the country launched ballistic missiles last month capable of reaching the U.S. The sanctions adopted unanimously by the Security Council over the weekend had the crucial support of China, North Korea’s chief economic partner, and Russia.

Mr. Ri’s statement rejected assertions by some Security Council members that North Korea’s military programs constituted a global threat and said they were instead a legitimate option for self-defense “in the face of a clear and real nuclear threat posed by the US.”

If the US attacks North Korea, the country “is ready to teach the US a severe lesson with its nuclear strategic force,” the statement said. Other countries were not being threatened unless they joined the US in a military attack, it said.

North Korea also vowed to forge ahead with its nuclear and military programs, in a statement from its mission to the UN In the statement, North Korea blamed the US for the sanctions and criticized the countries that had endorsed the resolution.

“The unwise conduct of the US will only speed up its own extinction,” North Korea said in the statement, adding that the US was getting “more frenzied and desperate” instead of learning to coexist with the country.

Diplomats said the reaction from North Korea showed that the new sanctions would have an impact. “Ultimately, the regime bears responsibility for these sanctions. They hold the key to creating conditions for their removal,” said the UK’s ambassador to the UN, Matthew Rycroft.

The sanctions are meant to close loopholes that have allowed the rogue regime to cultivate trade, financing and labor ties, thereby generating revenue to support its nuclear and military programs. The sanctions ban trade in coal, iron and other items with North Korea and bar countries from employing North Korean laborers and entering into joint ventures with Pyongyang.

The sanctions resolution aims to cut a third, or $1 billion, from North Korea’s annual foreign revenue.

Earlier Monday, Mr. Tillerson said that if North Korea wants talks with Washington, it must first stop launching missiles.

“That would be the first and strongest signal,” he said. “We have not had extended periods of time where they were not taking some type of provocative action by launching ballistic missiles.”

Asked how long a missile moratorium would have to last to be taken as a signal, Mr. Tillerson said, “We’ll know it when we see it.”

Mr. Tillerson said the next step for the US is to see that sanctions are fully enforced around the world. The US will monitor that carefully, he said, and have “conversations” with any country not fully embracing both the spirit of the sanctions and their “operational execution.”

On Monday, President Donald Trump received an intelligence briefing and spoke for an hour with Mr. Tillerson and Chief of Staff John Kelly to discuss North Korea, the White House said.

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At a dinner for conference attendees Sunday, North Korea‘s Mr. Ri told his South Korean counterpart that Seoul’s offer last month of talks lacked “sincerity,” Yonhap News reported, citing a South Korean government source. The offer came from the administration of new South Korean President Moon Jae-in, the country’s first left-leaning president in nearly a decade.

Sunday night, Mr. Moon requested a call with Mr. Trump, in which the two leaders discussed North Korea’s July 28 launch of an intercontinental ballistic missile, the White House said, as well as the UN sanctions.

Asia remains divided on how best to address North Korea’s effort to produce a long-range nuclear missile. Some experts say they believe North Korea could develop a missile capable of handling atmospheric re-entry as early as next year. It is uncertain whether North Korea has developed the technology to miniaturize a nuclear device for such a missile.

Australia and Japan said in a joint statement with the U.S. that they were pushing the international community to enforce sanctions and impose additional diplomatic and economic measures. China and Russia say they prefer diplomatic engagement with North Korea, despite supporting the sanctions, and have called on the U.S. to end military exercises in the Korean Peninsula.

Speaking in Manila on Monday, Chinese Foreign Minister Wang Yi stressed Beijing’s commitment to the Security Council’s resolution, but noted the potential economic impact on China.

“Given China’s traditional economic relationship with North Korea, the price paid in implementing the resolution will mainly be paid by China,” Mr. Wang was cited as saying in a statement posted Tuesday to the Foreign Ministry’s website.

Le Luong Minh, the Vietnamese secretary-general of the Association of Southeast Asian Nations, the conference host, said in an interview that most of its members “are not for unilateral [actions] and largely not for sanctions. We are for mutual existence.’’

The difference of opinion has left an opening for Kim Jong Un’s regime, experts say, because it is able to maintain enough diplomatic and economic ties to continue developing weapons while stopping short of agreeing to negotiate.

“We are all forgetting that North Korea has only one card to play and no amount of talking or sanctions will change their mind,” said James Chin, director of the Asia Institute at the University of Tasmania and an expert on North Korean sanctions evasion.

North Korea’s recent missile tests surprised the international community with their capability. One of the missiles would be able to fly more than 6,400 miles, according to one analysis, putting Los Angeles, Denver and Chicago within range.

In his statement, Mr. Ri said the North Korean regime was seeking nuclear capability as a deterrent and wouldn’t use the weapons against any country except the US unless another nation aided in an attack against North Korea.

Washington had sought the UN sanctions against Pyongyang to make the conflict an international issue, Mr. Ri said. The world was “becoming gradually aware of the danger” of Mr. Trump’s ”America First” policy of prioritizing US interests in international affairs, Mr. Ri added.

Mr. Tillerson meanwhile briefed allies Japan and South Korea on US efforts to urge countries in Africa, Asia and the Middle East to stop using North Korean contract labor, a US official said. The secretary called the practice “a human-rights concern because of the unfair treatment, trafficking conditions and misuse of wages,” according to the official.

The latest UN action makes clear that there is “no daylight among the international community as to the expectation that North Korea will take steps” to denuclearize the Korean Peninsula, Mr. Tillerson said. (wsj)