"Right now we see this process is making a negative contribution to the (Geneva) decisions," Russian Foreign Minister Sergei Lavrov told reporters in Istanbul, referring to a 2012 accord aimed at ending the conflict through talks between all parties.

"When one party is isolated in any mechanism set up to deal with a conflict, we miss the ground for dialogue," he said.

A Friends of Syria meeting is set for Istanbul on Saturday to be attended by US Secretary of State John Kerry as well as several of his Western and Arab counterparts.

Lavrov warned against any military intervention in Syria would only make the situation worse and encourage the spread of extremist groups such as Al-Qaeda.

 

"We see Al-Qaeda-related groups struggling against the current regime (in Syria), and that's a very worrying aspect," he said.

 

"And they are listed as terrorist groups by the United States," Lavrov added.

Last week, the head of terrorist Al-Nusra Front pledged allegiance to Al-Qaeda, in an announcement which is likely to bolster Damascus's argument that it is fighting "terrorists."