Rajaa al-Nasser of the National Coordination Committee for Democratic Changes in Syria (NCC) told the conference all Syrians should have a role in forging a new government.
Day Press News said representatives of 15 opposition parties and eight "civil society movements" attended the summit in Damascus, which was organized by the NCC.
One of the speakers was the Russian Ambassador to Syria Azamat Kulmukhametov, who said a cease-fire and open dialogue would open a path to an agreement to end the rebellion. "We are convinced that a dialogue without preconditions is the sole way out of the current crisis whose continuation bodes no good either for Syria or for the region as a whole," he said.
Envoys from various Arab nations as well as China and Iran also attended the meeting, Day Press News said.
Official Syrian media reported the summit was taking place with the goal of finding "ways to get Syria out of the crisis it faces."
Fighting continued across Syria Sunday. The opposition Syrian Network for Human Rights reported in a written statement that 14 civilians were killed Sunday, most from mortar and artillery fire.