US Secretary of State John Kerry and his Russian counterpart Sergei Lavrov on Saturday discussed who should represent the Syrian "opposition" at crucial talks with the government

US Secretary of State John Kerry and his Russian counterpart Sergei Lavrov on Saturday discussed who should represent the Syrian "opposition" at crucial talks with the government as time ticks down on the meeting scheduled for next week.

The talks -- part of the biggest diplomatic push yet to resolve a civil war which began almost five years ago -- were scheduled to open in Geneva on Monday.

But the United Nations has said they may be delayed several days amid intense wrangling over the makeup of the opposition delegation.

Kerry called Lavrov to discuss the talks following a face-to-face meeting on Wednesday, the Russian foreign ministry said in a statement, with both men backing efforts to get them started in Geneva "next week".

"Particular attention was given to the need to form a genuinely representative opposition delegation," the statement said.