GENEVA — Russian arms control officials left Geneva over the weekend for Moscow, but negotiations with the United States on a START successor treaty are expected to resume in coming weeks, an official said.

The pause appeared to signal that high-level consultations in the capital are needed on final details of the pact to cut strategic nuclear weapons, analysts said.

It comes after the presidents of Russia and the United States agreed Wednesday to urge their negotiators to speed up work and prepare for signing a new START deal.

"I don't know the new date of negotiations, maybe on March 8th or 15th," an official at the Russian diplomatic mission said.

Russian officials were to attend a negotiation session Saturday morning in the Swiss city before departing for Moscow, the official added.

There was no official confirmation of the break from the U.S. diplomatic mission in Geneva, where one American official said it had been under discussion by the two sides.

Presidents Barack Obama and Dmitry Medvedev have pledged to complete the pact to succeed the 1991 Strategic Arms Reduction Treaty, which expired in December. They have agreed to cut deployed nuclear warheads to between 1,500 and 1,675 on each side.

U.S. State Department spokesman P.J. Crowley said Tuesday that the United States believes that an agreement is now clearly in sight.

"There are still some details to be worked out. We hope we can do that in coming days," he told a news briefing in Washington after U.S. Secretary of State Hillary Clinton phoned Foreign Minister Sergei Lavrov to discuss the talks.

There has been a media blackout around the intense talks, which broke off for a few weeks for the Christmas and New Year holidays.

"The negotiators are closeted and practically living together," a Western diplomat in Geneva said last week.