Russia has started interacting with the United States and other countries on the Syria issue, U.S. Defense Secretary Leon Panetta said on Thursday, RIA Novosti reported.
"At this point, Russia has been cooperative" in negotiating a ceasefire designed to stop clashes between President Bashar al-Assad's forces and the opposition, Panetta said.
A ceasefire, part of UN envoy Kofi Annan's peace plan, came into force in Syria on April 12, although there have been reports of numerous violations of the truce by both government and opposition forces.
More than 9,000 people have been killed in Syria since the outbreak of a popular uprising against President Bashar al-Assad last March, according to UN estimates.
A group of six UN observers have been deployed to Syria to monitor the ceasefire in line with a resolution approved by the Security Council last week, which provides for a 30-strong monitoring mission to be sent to the violence-hit Arab country.
On Wednesday, U.N. Secretary-General Ban Ki-moon recommended the Security Council approve a mission of 300 observers - 50 more than originally planned.
Russia has twice vetoed UN Security Council resolutions on Syria over what it says is a pro-rebel bias, but gave its full backing to Annan's peace plan, which Damascus also supported.