US President Barack Obama is due to hold his first meeting with Russian Prime Minister Vladimir Putin.
Mr Obama's meeting with the man widely regarded as the most powerful in Russia will begin the second day of the American leader's visit to Moscow.
On Monday, Mr Obama and Russian President Dmitry Medvedev signed eight separate agreements.
They included a pact to negotiate a new arms control treaty to replace the 1991 Start I pact which expires in December.
A new agreement could see the two countries reducing their nuclear warheads by up to the third, to below 1,700 each within seven years of the treaty's signing.
'Old ways'
Also on Tuesday, Mr Obama is due to deliver a major speech on democracy, the global economy and the US-Russian relationship.
US-RUSSIA NUCLEAR DEAL
Each country to cut deployed nuclear warheads to 1,500-1,675 (currently 1,700-2,200)
Delivery systems to be within 500-1,000 range (currently 1,600)
Reductions so be achieved within seven years of new treaty
Treaty to be signed before Start I expires in December and include "effective" verification measures
See graph of US and Russian nuclear weapon stockpiles
Mr Obama said last week that he thought Mr Putin, the former Russian president turned prime minister, had "one foot in the old ways of doing business and one foot in the new".
Mr Putin responded: "We stand solidly on our own two feet and always look into the future."
But on Monday, the US leader struck a more diplomatic tone.
"My interest is in dealing directly with my counterpart, the president [Medvedev], but also to reach out to Prime Minister Putin and all other influential sectors in Russian society," Mr Obama was quoted as saying by Reuters news agency.
A BBC correspondent at Monday's talks said the two presidents seemed to have taken a significant step towards improving US-Russian relations, which have been badly strained in recent years.
Separately, Russia also agreed to allow the US military to fly troops and weapons across its territory to Afghanistan, allowing it to avoid using supply routes through Pakistan that are attacked by militants.
However, on the contentious issue of US plans to base parts of a missile defence shield in Eastern Europe, the presidents merely said they had agreed to a joint study into ballistic missile threats and the creation of a data exchange centre.
Graph showing US and Russian nuclear weapon stockpiles