MOSCOW: Russia on Thursday accused the United States of slowing down talks on a new nuclear weapons disarmament treaty, but Washington insisted it still aimed to sign a new accord this year.

US and Russian officials have been holding intense talks in Geneva on replacing the 1991 Strategic Arms Reduction Treaty which led to deep cuts in their nuclear arsenals but expired on December 5 without a replacement.

"In the past couple of days we have noted a slowdown in the positions of the US negotiators in Geneva," Russian Foreign Minister Sergei Lavrov said.

Lavrov dismissed reports suggesting a new treaty would be signed at the UN climate summit in Copenhagen, which ends Friday and will be attended by both US President Barack Obama and Russia's Dmitry Medvedev.

Medvedev and Obama had first pledged to sign the successor treaty by the time the original agreement expired on December 5.

Then the officials on both sides said the deal would be signed by end of the year, possibly in a European capital.

"It is highly unlikely to happen in Copenhagen," Lavrov said at a press conference in Moscow. "The work is continuing. A lot of key issues have already been agreed upon but some things remain to be solved."

"If the negotiators -- both Russian and American -- concentrate on fulfilling the instructions of the presidents, we will achieve an agreement fairly quickly," he added.

But the White House responded by saying that progress was being made and that a deal could be signed by the new year.

"Our goal remains to conclude a good and verifiable agreement by the end of the year," said National Security Council spokesman Michael Hammer.

"Presidents Obama and Medvedev have instructed their delegations to work intensively towards reaching a post-START agreement and we are making progress."

Replacing START appears to be turning into an embarrassment as Russia and the United States have broken a series of deadlines to agree the deal.

"The new START treaty has not been signed on time," Newsweek's Russian edition said this week. "Dmitry Medvedev and Barack Obama will not manage to become friends."

Citing diplomatic sources, the magazine said the US team had hinted it wanted to sign the agreement by the time Obama was to receive the Nobel Prize on December 10 but Russia's powerful premier Vladimir Putin had convinced Medvedev "not to hurry."

Moscow has interpreted the US request as an opportunity to arm twist Washington to win more concessions, a move that soured the talks, it said.

Lavrov indicated Thursday the talks might be losing the momentum. "They (the US officials in Geneva) are referring to the necessity to receive additional instructions" from Washington, he said.

On Wednesday, a State Department official, speaking on condition of anonymity, told reporters not to expect the deal with Russia before the year's end.

A Kremlin official, speaking to AFP on condition of anonymity Thursday, refused to say when the agreement would be signed.

Asked what the delay in signing was caused by the official said: "Nothing. The agreement is almost ready. Just running out of time in terms of organisation."

An informed source in Moscow told the Interfax news agency Thursday that "the number of details that need to be agreed is such that it's physically impossible to do it all in the time left until the end of the year."

Some observers have speculated Russia is deliberately throwing the wrench in the works to prolong the talks.

"If there were political will, the agreement could be signed at any moment," Alexander Golts, an independent defence analyst, told AFP.

But others like Fyodor Lukyanov, editor of the Russia in Global Affairs magazine say the two sides have to make sure no one can "pick holes" in the new document so that it can be ratified both in Moscow and Washington.

"It's good there is no rush," Lukyanov said.