Moscow and Washington made a joint call to Syria's regime and the opposition forces yesterday for ceasefires in parts of the country ahead of peace talks next week.
But the two countries continued to disagree on Iran's participation in the talks, with US Secretary of State John Kerry saying Tehran needs to accept plans for a transitional government if it wants to take part.
Meeting in Paris with UN-Arab League envoy Lakhdar Brahimi, Kerry and Russian Foreign Minister Sergei Lavrov called for the ceasefires to start ahead of the Geneva II talks due to begin in Montreux a week tomorrow.
It was a rare pulling together of two heavyweights in the Syrian crisis, which has seen the US backing the opposition as Moscow sticks by longtime ally President Bashar al-Assad.
Kerry said: "We talked today about the possibility of trying to encourage a ceasefire, maybe a localised ceasefire beginning with Aleppo (in the north)."
Washington and Moscow are hoping to build momentum ahead of the talks, which are seeking to revive efforts to hammer out a deal on moving to a transitional government after a three-year conflict that has killed 130,000 people.
Damascus' ambassador to Moscow said yesterday that Syrian Foreign Minister Walid Muallem will also visit Russia ahead of the talks.
Lavrov said the Assad regime had indicated it was ready to allow access for humanitarian aid, citing the embattled Damascus suburb of East Ghouta, where thousands have been trapped.