UNITED NATIONS - US Secretary of State Mike Pompeo warned Thursday that sanctions against North Korea must be “vigorously” enforced, during a Security Council meeting attended by the foreign ministers of Russia and China.

“Enforcement of UN Security Council sanctions must continue vigorously and without fail until we realize final, fully-verified denuclearization,” Pompeo said.

Days before he is due to fly to Pyongyang to push ahead with what would have been an unimaginable project a year ago, Secretary of State Mike Pompeo will portray his boss Donald Trump’s unconventional diplomacy as the main reason for a dramatic turnaround.

China and Russia called Thursday for an easing of sanctions against North Korea , rejecting a US call at the UN Security Council to press on with vigorous enforcement despite a dip in tensions. Led by the United States, the Security Council adopted three sanctions resolutions last year aimed at depriving North Korea of revenue for its nuclear and ballistic missile programs.

Chinese Foreign Minister Wang Yi told a council meeting that the thaw in relations between North and South Korea - combined with warmer US-North Korean ties - should lead to sanctions relief.

“Given the positive developments,” Wang said the council should consider a provision to “modify the sanctions measures in light of the DPRK’s compliance.”

Russia backed China’s call to consider a sanctions review. Declaring that sanctions should not become a form of “collective punishment,” Russian Foreign Minister Sergei Lavrov argued that it was time to send a positive signal to Pyongyang to encourage concessions.

“Steps by the DPRK toward gradual disarmament should be followed by an easing of sanctions,” said Lavrov. US Secretary of State Mike Pompeo opened the meeting, held during the annual UN General Assembly session, by demanding strict enforcement of sanctions.

Pompeo - who will pay his fourth visit to Pyongyang next month - voiced hope for the “dawn of a new day” with Pyongyang, but credited sanctions with bringing North Korea to the table and said there should be no let-up in pressure.

“Enforcement of UN Security Council sanctions must continue vigorously and without fail until we realize final, fully verified denuclearization,” Pompeo said.

“The members of this Council must set the example on that effort, and we must all hold each other accountable.” In thinly veiled criticism of China, which is by far the most important trading partner of North Korea , Pompeo said sanctions have been repeatedly violated - including, this year already, its annual cap of importing 500,000 barrels of oil.

Pompeo said the United States had also detected inter-ship transfers of refined petroleum, which is also banned under UN sanctions, and said that North Korea was illegally exporting coal to fund its weapons program. He also criticized Russia for bringing in workers from North Korea - which human rights groups consider a vital source of hard currency for the regime, with the laborers often working in slave-like conditions on construction sites. China, which has fast-deteriorating relations with US President Donald Trump yet has largely welcomed his outreach to North Korea , stressed the need for diplomacy.

“China firmly believes that pressure is not the end,” Wang said. “Both implementing sanctions and promoting political settlement are equally important.”

Lavrov said it was “inappropriate and untimely” for the United States and its partners to “impose a course of tightening sanctions” when North Korea has “taken important steps” toward denuclearization. “It seems it would be logical to strengthen this momentum,” said Lavrov.

The Russian foreign minister also accused the United States of hypocrisy after Trump abandoned an international agreement on Iran, which drastically cut back its nuclear program in exchange for sanctions relief.

North Korean representatives attended the Security Council session, but they did not ask to speak.

On Wednesday, Pompeo met his North Korean counterpart, Foreign Minister Ri Yong Ho, and called the talks “very positive.”

Trump has heaped praise on North Korea’s Kim Jong Un, one of the world’s most repressive leaders, and boasted that his diplomacy has prevented war.

But underlying US calculations, many analysts doubt that North Korea has shifted more than rhetorically after already refining its arsenal through six nuclear tests since 2006 and repeated rocket launches.

The United States is also hearing calls for step-by-step sanctions relief from ally South Korea, whose left-leaning president, Moon Jae-in, helped arrange Trump’s diplomatic drive.

Trump met Kim in June the first-ever summit between the two countries that never signed a peace treaty.

Trump is seeking a second summit in the near future, whichPompeo will seek to arrange while in Pyongyang.

Pompeo said that North Korea would enjoy a “much brighter future” if Kim fulfills promises to the United States to give up its nuclear and ballistic missile program.

“But the path to peace and a brighter future is only through diplomacy and denuclearization,” Pompeo said. “That means any other path North Korea may choose will inevitably lead to ever-increasing isolation and pressure.”