BEIRUT — Syrian rebels launched a dawn assault Saturday on a strategic airbase in the north of the country, trying to disrupt strikes by warplanes and helicopters that pound rebel-held towns and give the regime of President Bashar Assad a major edge in the civil war.

The assault, reported by activists, comes a day before the start of a key international conference in Qatar at which the United States and its allies aim to reorganize the opposition’s political leadership and unite their ranks. The leadership-in-exile has been widely seen as ineffective and out of touch with rebel fighters on the ground.

Rebel forces attacked the Taftanaz airbase early Saturday morning in fighting with government forces that continued into the afternoon, the anti-regime activist Syrian Observatory for Human Rights said.

The Taftanaz base mainly houses military helicopters, near the main highway between the capital Damascus and the northern city of Aleppo, where rebels and the military have been battling for control for months.