MOSCOW — Russia on Thursday accused the Arab League of abandoning support for a peaceful solution to the conflict in Syria and said it had cast doubt over the mandate of U.N.-Arab League mediator Lakhdar Brahimi by giving a summit seat to the Syrian opposition.

Opposition leader Moaz Alkhatib took Syria's vacant seat on Tuesday at the Arab summit, which also has lent its support to giving military aid to rebels fighting President Bashar al-Assad.

"We view the results of the Arab League summit in Doha with regret. The main meaning of the decisions that were made there is that the Arab League has rejected a peaceful solution," Foreign Minister Sergei Lavrov said.

Russia, which has long supplied arms to Assad's government but says it is not delivering weapons that could be used in the civil war, has vehemently opposed arming the rebels.

Moscow says it has pressed Assad to end violence and accuses Western and Arab states of failing to put enough pressure on his opponents to do so, even encouraging them to keep fighting.

"A huge question emerges as regards the mandate of Lakhdar Brahimi, who until the summit was the U.N. and Arab League representative for promoting contacts and talks between the government and opposition," Lavrov said.

"I just don't see how Mr. Brahimi can continue to be considered the representative not just of the United Nations but of the Arab League," he told a joint briefing after talks with Thai Foreign Minister Surapong Tovichakchaikul.

Russia has vocally supported Brahimi, who has met in recent months with Russian and U.S. officials as part of an effort to end the violence that has killed more than 70,000 people in two years. But those talks did not bridge disagreement between Moscow and Washington over Syria.

Brahimi and U.N. Secretary General Ban Ki-moon voiced regret over the lack of progress earlier this month. Russia and China have blocked three resolutions in the U.N. Security Council, and Moscow says Assad's exit from power must not be a precondition for peace talks.