The US and Russia say they will try to clinch a new strategic arms reduction treaty (Start) by the end of 2009.
“This is of the highest priority,” US Secretary of State Hillary Clinton said, after talks in Geneva with her Russian counterpart Sergei Lavrov.
In turn, Mr Lavrov described the current Start treaty – due to expire by 5 December – as “obsolete”.
Mrs Clinton earlier said Washington was keen to re-launch its ties with Moscow to end months of cool relations.
Start 1 limited the deployment of nuclear warheads to 6,000 per side, along with 1,600 missiles and bombers.
It was followed by Start 2 which brought warheads down to 3,500.
Mrs Clinton and Mr Lavrov said the two sides had agreed to work together on a number of issues of common and world interest, including Afghanistan, the Middle East and North Korea.
But the two diplomats admitted that differences in their positions remained.
Mrs Clinton said the relationship between the two countries needed “more trust, predictability and progress”.
After the talks, Mr Lavrov later told the 65-nation UN Conference on Disarmament in Geneva: “The right moment has come, for the first time since the end of the Cold War, for making real progress in resuming the global disarmament process on a broad agenda.”
The BBC’s Imogen Foulkes in Geneva says agreement on the need for a new deal to cut warheads and delivery systems by the end of this year is the easiest disarmament move the two sides can make at this point.
Other more divisive issues remain, says our correspondent, such as Washington’s plan for a missile defence shield in Eastern Europe – Moscow strongly objects to this.
But, Sergei Lavrov said, talks are continuing on this too, and compromise might be possible.
Our correspondent says it is at least a sign the UN disarmament process, in stalemate for so long, is now moving again, amid warming relations between Moscow and Washington.
On Thursday, Nato agreed to resume high-level contacts with Russia, especially regarding co-operation over the Nato mission in Afghanistan.
Relations between the US and Russia have deteriorated in recent years over Russia’s role in the war in Georgia, American support for the entry of Georgia and Ukraine to Nato, and the planned US missile shield based in central Europe.