The UN mediator for Syria Staffan de Mistura and Russian Deputy Foreign Minister Gennady Gatilov are due to come together in Geneva on Monday to discuss ways to revive a tattered ceasefire in Syria.
Points discussed in their meeting will be evaluated in another meeting in the Kazakh capital Astana on May 3-4 in talks organised by Russia, Iran and Turkey.
The United States made it clear that it had no intention of taking part in Monday's meeting, de Mistura told reporters last week.
Tensions between Russia and the US remain high due to differences over the Syrian conflict. While Russia backs Bashar al Assad's regime, the US has supported opposition forces.
Relations between Washington and Moscow hit an all-time low after US warships in the eastern Mediterranean carried out a missile strike on a regime air base this month.
The strike was in retaliation for a chemical weapons attack, allegedly carried out by regime forces located at the base, that killed scores of people near Idlib on April 4.
However, the US has expressed willingness to participate in trilateral meetings which include Russia at a later date, de Mistura informed reporters.
"The US welcomes discussions with Russia regarding the UN-led political process on Syria in Geneva, and we have met in the past in the trilateral US-Russia-UN format," a US spokesman in Geneva said in an email.
"But at this time there is no new trilateral meeting scheduled," the spokesman added.