Washington/Moscow, Dec 5 : The US and Russia will adhere to a nuclear arms reduction treaty even as it is set to expire, as negotiators from the two countries continue work on a new agreement.

US President Barack Obama and Russian President Dmitry Medvedev issued a joint statement Friday pledging to work together "in the spirit of the START Treaty following its expiration."

US and Russian officials have been intensely negotiating a successor to START, or the Strategic Arms Reduction Treaty, which was signed in 1991. But it appears they will miss the goal of wrapping up a new agreement when the current one runs out on Saturday.

Obama and Medvedev voiced their "firm intention to ensure that a new treaty on strategic arms enter into force at the earliest possible date."

Obama's national security adviser, James Jones, told reporters Friday that a new agreement could come in "two or three days or a couple weeks."

"We are in the final moments," he said, adding "there is no reason to think this won't be done."

The goal of the new accord is reportedly to reduce the number of nuclear warheads to a maximum of 1,675 per country, while limiting delivery systems to 1,100 each. Any new treaty would have to be ratified by the US Senate and Russian Duma.

US State Department spokesman Ian Kelly told reporters that the negotiations have produced "good progress" and that an agreement has been reached on the "basic framework" and "major provisions" of the treaty. He would not elaborate on remaining differences.

"There have been some very robust discussions about some of the differences that we have," Kelly said. "Both sides agree that we need to resolve these in the next few weeks." (DPA)