Two other diplomats, who also spoke on condition of anonymity, said a vote on the resolution that had been expected on Friday had been postponed at the request of the United States to allow for further consultations.

The first diplomat said a Russian veto would mean dissolution of the Panel of Experts monitoring enforcement of long-standing U.N. sanctions against North Korea over its nuclear weapons and ballistic missile programs.

"It's a strong possibility that Russia vetoes this resolution," the diplomat said. "That's unprecedented - basically it's been technical roll-overs for the last 14 years, I believe."

Russia's mission to the United Nations did not immediately respond to a request for comment.

Earlier on Friday, Russia, along with China, voted against a U.S.-proposed Security Council resolution calling for an immediate ceasefire and an Israel-Hamas hostage deal.

Postponement of the North Korea vote came as news spread about an attack by gunmen on a concert near Moscow in which at least 40 people were killed and more than 100 hurt, one of the worst such attacks on Russia in years.

A text of the North Korea resolution seen by Reuters calls for the extension of the mandate of the Panel of Experts for another year, until April 30, 2025.

Another U.N. diplomat said that both Russia and China had sought "sunset" clauses to parts of the sanctions regime on North Korea and the text states the Security Council "is prepared to review, by 30 April 2025, the appropriateness of measures taken to date."

Such a review would cover possible "strengthening, modification, suspension, or lifting of the measures as may be needed in light of (North Korea's) compliance," it said.

The suggestion of a possible Russian veto comes after a closening of relations between North Korea and Russia since Moscow's 2022 invasion of Ukraine.

The United States has charged that North Korea has supplied Russia with large quantities of artillery shells as well as ballistic missiles for use in Ukraine. Russia and North Korea have denied this even as they pledged to strengthen military cooperation.

Last year Russia voted in favor of an extension of the mandate of the Panel of Experts, but expressed regret that the resolution then did not include proposals on the need to minimize the impact of sanctions on the North Korean population and confidentiality issues concerning the panel.

Years of U.S.-led international sanctions have failed to halt North Korea's nuclear bomb and missile programs and many North Korea watchers consider the U.N. regime, supported in the past by China and Russia, especially after North Korean nuclear bomb tests, moribund, if not already dead.

"Sanctions, by many accounts, are already effectively dead, if major players aren't enforcing or implementing them," said Jenny Town, director of the Washington-based North Korea monitoring program, 38 North.

North Korea has long been banned from conducting nuclear tests and ballistic missile launches by the 15-member Security Council. Since 2006, it has been subject to U.N. sanctions, which the council repeatedly strengthened to try and cut off funding for its weapons of mass destruction development.