The United States will stop complying with a landmark nuclear pact with Russia as soon as this weekend after last-ditch talks with Moscow to save it fell flat, a senior U.S. arms control official said on Thursday.

Washington has long accused Russia of flouting the 1987 Intermediate-range Nuclear Forces Treaty (INF), alleging that a new Russian missile, the Novator 9M729, called the SSC-8 by NATO, violates the pact, which bans either side from stationing short- and intermediate-range, land-based missiles in Europe.

Russia denies that, saying that the missile’s range puts it outside the treaty, and has accused the U.S. of inventing a false pretext to exit a treaty Washington wants to leave anyway so as to develop new missiles. It has also rejected a U.S. demand to destroy the new missile.

60-day deadline

U.S. Under Secretary of State for Arms Control and International Security Andrea Thompson on Thursday held last-ditch talks with Russian Deputy Foreign Minister Sergei Ryabkov in Beijing, ahead of the expiration of a 60-day deadline for Moscow to come back into compliance with the treaty.

Ms. Thompson and Mr. Ryabkov, who met on the sidelines of a P5 meeting of nuclear powers, said afterwards that the two countries had failed to bridge their differences.

In an interview, Ms. Thompson said she expected Washington to now stop complying with the treaty as soon as this weekend.

The formal withdrawal process, once announced, takes six months.

Mr. Ryabkov said Moscow would continue working to try to reach agreement despite the failure of the talks, but accused Washington of ignoring Russian complaints about U.S. missiles and of adopting what he called a destructive position.