VIENNA, Oct 31 : Russia has warned of the risk of a "proxy war" in the Middle East after the US said it would send special forces to Syria.
Russian Foreign Minister Sergei Lavrov said this increased the need for cooperation between the US and Russia.
US officials said "fewer than 50" troops would "train, advise and assist" vetted opposition forces in fighting the so-called Islamic State (IS). It will be the first time that US troops operate openly in Syria.
Lavrov said the US had decided on its move "unilaterally and without any reference to the Syrian leadership".
He added: "I am convinced that neither the United States nor Russia of course want any kind of slide into a so-called proxy war. But to me it is obvious that this situation makes the task of cooperation between the militaries even more relevant."
He was speaking after talks with US Secretary of State John Kerry and UN envoy for Syria Staffan de Mistura in Vienna.
"Our role fundamentally and the strategy is to enable local forces but does that put US forces in harm's way? It does, no question about it," Defence Secretary Ash Carter later told reporters.
He did not rule out further deployments of special forces to the region, if the initial mission was deemed a success.
For more than a year, US-led coalition forces have been carrying out air strikes against IS, which controls a large part of northern Syria and parts of neighbouring Iraq.
This week's talks in Vienna involved Iran for the first time.
The summit sought to close the gap between the US and its allies, who support the rebels, and the key foreign allies of the Syrian government, Russia and Iran.
World leaders say progress was made in the "historic" talks to resolve Syria's civil war, but they continue to differ on the fate of President Bashar al-Assad.
Meanwhile, major powers meeting in Vienna for talks on Syria have found enough "common ground" to meet for a new round of talks in two weeks, even as the conflict enters a new phase with the deployment of US special forces in the country.
The troop announcement came as diplomats in the Austrian capital representing 17 countries and the EU agreed to launch a broad new peace attempt to gradually end Syria's long civil war - a declaration that avoided any decision on when President Bashar al-Assad might leave.
It is not clear how many rebel groups would agree to a plan that does not result in Assad's immediate departure.
Representatives from Britain, Egypt, France, Germany, Italy, Lebanon, the EU and other Arab states also attended. The participation by Russia and Iran in the attempt could mark a new and promising phase in the diplomacy since those countries have staunchly backed Assad. ?BBC, AL JAZEERA