Syria's national airline canceled a flight to Aleppo on Saturday because of fighting near its international airport, while the United Nations top envoy to the country said it faced "hell or a political process" but gave no sign a truce was in sight.
The two developments underscored just how far international efforts to end the violence in Syria have fallen behind developments on the ground, more than 21 months into the conflict.
Speaking in Moscow, Lakhdar Brahimi, who represents the U.N. and the Arab League, warned that the civil war could spread chaos in the region by sending streams of refugees into neighboring countries.
Since starting his job in September, Brahimi has sought to advance an international plan that calls for an open-ended cease-fire between rebels and government troops and the formation of a transitional government to run the country until elections can be held.
After a trip to Damascus last week and talks with Russian officials, Brahimi said a truce is the country's only way out.
"If the only alternative is really hell or a political process, then we have got all of us to work ceaselessly for a political process," he said.
But neither side appears interested in the plan. The rebels reject any efforts that do not call for the ouster of President Bashar Assad, and Assad's government is unlikely to give up power voluntarily. It has not commented on Brahimi's plan.
Speaking alongside Brahimi, Russia Foreign Minister Sergey Lavrov said his government would continue to refuse any plan that calls for Assad's ouster and that Assad had repeatedly said he would not step down.
"There is no possibility to change that stance," he said.
He criticized the opposition's insistence on Assad's departure as "counterproductive."
"The price for that precondition will be the loss of more Syrian lives," he said.
Russia has long been Assad's biggest international backer, selling arms to his forces and, along with China, protecting Syria from sanction by the U.N. Security Council.
Russia has called for a negotiated solution to the conflict, while top officials appear increasingly resigned to Assad's possible ouster by rebel forces.
Violence continued around Syria on Saturday.
Cairo airport officials said a flight that was supposed to stop in Aleppo before continuing to Damascus flew straight to Damascus "because of the deteriorated security situation" near the Aleppo airport.
It was the first time a flight to Syria's largest city had been canceled because of fighting near the airport, they said. The Syrian government and its airline did not comment.
Rebels seeking to topple President Bashar Assad have launched a campaign to seize government airports as a way to cut the regime's supply lines and strike a blow against its air power, the biggest threat faced by rebel forces.
While the rebels have yet to seize a major airport, they have disrupted traffic at some with heavy machine-gun fire, and flights to Damascus have been canceled due to fighting near its airport.
Syrian airlines is the only carrier still flying to Damascus, running one flight per day, though some officials still consider the trip too risky.
Last week, Brahimi flew into Beirut and drove to Damascus overland to avoid the airport. On Saturday, Lebanese security officials said Syrian Deputy Foreign Minister Faisal Mekdad did the same while returning from Moscow.
The officials spoke on condition of anonymity because they were not authorized to brief the media.
Aleppo's international airport is just southeast of the city and still controlled by the government. It sits next to the Nerab military airport. The base of the army's 80th Brigade is nearby.
Rebels have been clashing with government troops near the airport for days, and videos posted online show them firing homemade rockets and shooting at targets inside. The videos appeared genuine and corresponded to other reporting by The Associated Press.
An Aleppo activist said the area's rebels see the airport's capture as a clear way to weaken regime forces fighting in the city since it is used to bring in supplies.
"Since the rebels have targeted all the supply roads, the airport is the main way for forces in the city to get supplies, so if they can take it over it will be a big blow to the regime," the activist said via Skype, speaking on condition of anonymity out of security concerns.
He and other activists reported a large explosion inside the airport on Friday, though it was unclear what caused it.
Illustrating the danger of the government's air power, anti-regime activists reported a number of deadly airstrikes in different parts of Syria, including in the towns of Azaz and Tel Rifat north of Aleppo and al-Nishabiyeh, south of Damascus.
Rebels also clashed Friday with soldiers inside the Mannagh helicopter base near the Turkish border.
Anti-regime activists say more than 40,000 people have been killed since the start of Syria's crisis in March 2011.
Associated Press writers Maamoun Youssef in Cairo and Vladimir Isachenkov in Moscow contributed reporting.