Syrian rebels launched a counteroffensive in the northern city of Aleppo, recapturing a base near its international airport hours after Syria’s army advanced into the area, activists said Saturday.

The fighting came as the main Western-backed opposition group began a two-day meeting in Istanbul to decide whether it would attend a peace conference the United States and Russia are trying to convene in Geneva.

The Syrian National Coalition has demanded that President Bashar al-Assad step down in any transitional Syrian government as a condition for going to Geneva. Syrian officials say that Assad will stay in his post at least until his term ends in 2014 and that he may run for reelection.

In Cairo, Arab League head Nabil Elaraby told reporters that the U.N.-Arab League’s top envoy to Syria, Lakhdar Brahimi, will hold a meeting in early December to decide on a new date and the attendees of the Geneva conference.

“We were saddened and depressed because of the failure of the latest meetings to decide on a date and participants for the conference,” Elaraby said, referring to a meeting in Geneva in the past week that many had hoped would result in a call for holding the talks this month. The league had wanted the peace conference to lead to a cease-fire and secure means to deliver humanitarian aid to Syrians, Elaraby said.

In Aleppo, al-Qaeda-linked rebels and other Islamist fighters recaptured the Brigade 80 base that had protected the city’s airport, the Britain-based Syrian Observatory for Human Rights and the Aleppo Media Center said. The government has not confirmed losing the base.

The government-held Aleppo International Airport, which has been closed by the fighting for almost a year, is one of the Syrian rebels’ major objectives.

Brigade 80 first fell to rebels in February, but government troops seized parts of it early Friday. The rebels launched a push to retake it that day, and fighting continued into Saturday, with 20 government soldiers killed as well as more than 40 rebels from different groups, including al-Qaeda’s Jabhat al-Nusra and the Islamic State of Iraq and Syria, according to the Syrian Observatory for Human Rights.

Syria’s state-run news agency SANA said a rocket fired by opposition fighters hit near a health center in Aleppo’s Ashrafieh neighborhood, killing six children and wounding six others.

— Associated Press