(Reuters) - Syria's opposition leader has rejected an invitation from Russia for peace talks, dealing another blow to international hopes that diplomacy can be resurrected to end a 21-month civil war.

Russia, President Bashar al-Assad's main international protector, said on Friday it had sent an invitation for a visit to Moaz Alkhatib, whose six-week-old National Coalition opposition group has been recognized by most Western and Arab states as the legitimate voice of the Syrian people.