The acrimonious meeting of the Security Council was called by U.S. Ambassador Nikki Haley, who accused Russia of pressuring independent U.N. experts to alter a report on implementation of sanctions against North Korea that she said contained "evidence of multiple Russian sanctions violations."

The sharp disagreement marked a rare break in what has been a united response by the U.N.'s most powerful body to North Korea's escalating nuclear and ballistic missile programs.

It has unanimously imposed increasingly tough sanctions on Pyongyang that have cut off all North Korean exports, 90 percent of its trade, and disbanded its pool of workers send abroad to earn hard currency.

Haley said Russia's violations are "systematic," including ship-to-ship transfers of banned items, mainly oil but increasingly coal and other goods. She identified the Russian ship Patriot filmed transferring refined petroleum to a North Korean vessel and accused Moscow of trying to cover up violations "whether they're committed by Russia or citizens of other states."

Haley said the United States prevented publication of the "tainted" report that removed allegations against the Russians and demanded the release of the initial version.

Russian Ambassador Vassily Nebenzia countered that the work of the panel of experts "became increasingly politicized, then became ultimately the hostages to the vision of Washington" and didn't take into account Russia's views.

"Unsurprisingly, therefore, we insisted on having our position reflected in the document," he said, and a compromise on the report was reached among all 15 council members — including the "American delegation" and U.S. "experts."

But Nebenzia said Haley put a hold on the report the following day, so it is the United States that is blocking release of the report and "the ball now is in your court."

The U.S. Mission said later in a statement: "Certainly no U.S. expert agreed - at any point in the process - to Russia's tainted version of the report."

Behind the U.S.-Russia squabble over implementing sanctions are the broader issues of how to achieve denuclearization of the Korean peninsula and when sanctions should be lifted.

The United States has kept up sanctions pressure on the North despite the historic summit between President Donald Trump and North Korean leader Kim Jong Un in June that dialed down nuclear tensions between the adversaries. That first-ever meeting of leaders from the two countries has been followed by a diplomatic impasse over how to achieve the agreed-upon goal of denuclearization.

The U.S. has said sanctions won't be lifted until that goal is met. South Korean officials who recently met with Kim said he still has faith in Trump's commitment to ending their nations' hostile relations, but is frustrated by questions about his willingness to denuclearize and wants his "goodwill measures" to be met in kind.

Haley told the council that "the difficult, sensitive talks with North Korea are ongoing."

"The Trump-Kim summit has set us on the path toward complete denuclearization," she said. "But we are not there yet. And until we get there, we must not ease the powerful worldwide sanctions that are in place."

Nebenzia countered that "resolving the nuclear issue of the peninsula through just sanctions and pressure on Pyongyang is impossible." He charged that the U.S. is using the Security Council committee monitoring implementation of sanctions "as a sledgehammer to punish (North Korea) for their intransigence."

He cited welcome developments, including the North's suspension of missile and nuclear tests, dismantling of a missile engine test site, opening of a liaison office, and agreeing to a third summit of Kim and South Korean President Moon Jae-in starting Tuesday.

Noting difficulties in U.S.-North Korea negotiations, Nebenzia stressed that negotiations are "a two-way street."

"It is difficult to come to agreement if you offer nothing in return for your demands," he said.

"What can we expect when Pyongyang is being called upon to unconditionally agree to comply with all of the conditions against a guarantee of empty promises," Nebenzia asked, saying the U.S. has broken promises to Tehran and pulled out of the 2015 Iran nuclear deal.

He called for "confidence-building measures," citing as a possibility the signing of a peace treaty to end the 1950-53 Korean War. Nebenzia said the Security Council also could consider creating temporary exemptions from sanctions to carry out projects promoting inter-Korean cooperation.

Chinese Ambassador Ma Zhaoxu said Beijing remains committed to implementing both sanctions and dialogue.

"Confrontation is a dead end," he said. "Resorting to force will bring nothing but disastrous consequences to the peninsula."

China, which is North Korea's closest ally and is responsible for 90 percent of its trade, believes the Security Council should take action to reverse sanctions "at the appropriate time" in light of Pyongyang's progress to denuclearization.

"This council should stay united, honor its responsibility entrusted by history and push for the denuclearization and lasting peace in northeast Asia," Ma said.