Russia says it is ready to help US-backed rebels in Syria in their battle against militant organisations like the Islamic State group.
Foreign Minister Sergei Lavrov said the Russian air force could support the Free Syrian Army provided the US shares information about rebel positions.
The FSA has so far been among the rebel groups targeted by Russian strikes which have drawn Western criticism.
Russia is a key ally of Syrian President Bashar al-Assad.
It has been bombing targets in Syria since last month and says it is primarily hitting IS positions.
But Western powers say most of the air strikes have hit the FSA and other factions backed by the West and Gulf states.
In a TV interview, Lavrov said that the refusal of the US to co-ordinate their anti-terrorism campaign with Russia had been “a big mistake”.
The foreign minister said that in addition Russia was ready to support the FSA, but was hampered in doing this because the US was refusing to provide information about rebel and IS positions.
He said that a “correct understanding” of developments in war-torn Syria was emerging among Western politicians amid Europe’s migrant crisis.
The interview was recorded before talks on Friday with US Secretary of State John Kerry in Vienna. The transcript was released on Saturday.
Kerry said the talks had been “constructive” and that an expanded round of negotiations could take place next week.
On Thursday, President Putin suggested the Syrian regime could be ready to work with some rebel groups against IS.
Putin said President Assad had agreed to the idea on a recent visit to Moscow.
The US, Turkey and Saudi Arabia all support rebel groups fighting the Syrian government.
Russia backs President Assad, whose visit to Moscow on Tuesday was criticised by the US.