A Russian foreign ministry spokesman told AFP this week Syrian government and opposition representatives would meet for peace talks in Moscow on April 6.
But the exiled Syrian National Coalition said yesterday that it had discussed the invitation during a meeting of its members in Istanbul and "decided not to take part in the Moscow 2" talks.
Despite this, a coalition source told AFP the invitation was in itself "a major development" because it indicated that key Assad ally Russia "recognises the Coalition".
The National Coalition is the key political representative of Syria's opposition and is officially recognised by much of the international community.
It has participated in several rounds of failed peace talks, including two in Geneva, and insists that Assad must step down.
In January, Russia hosted talks aimed at finding a solution to the four-year-old conflict in Syria that was not attended by the National Coalition.
Earlier this month Russian Deputy Foreign Minister Gennady Gatilov said members of the National Coalition were "considering coming to Moscow" for the next meeting.
But Abdo on Saturday expressed concern at what he saw as an attempt to override what was said in Geneva.
He said the Coalition had decided to boycott the Moscow talks because of "the lack of a clear agenda, the absence a clear point of reference for anything that might be decided and the Coalition's refusal to engage in dialogue with the regime if this is not part of a transition process".
