GAZIANTEP, TURKEY - The Obama administration is warning Russia that their military cooperation in Syria will not go forward unless humanitarian aid begins to reach Aleppo and other besieged areas.

In a statement released by the State Department, Secretary of State John Kerry told Russian Foreign Minister Sergei Lavrov that the U.S. has "concerns about the repeated and unacceptable delays of humanitarian aid, and emphasized that the United States expects Russia to use its influence on the Assad regime" to allow the deliveries to move forward.

US Warns Russia Cease-fire Depends on Aleppo Aid

Russian warplanes Friday launched airstrikes on a rebel base in Aleppo. Russian officials said they did so because of rebel refusal to pull back from a key road leading into eastern Aleppo.

US Warns Russia Cease-fire Depends on Aleppo Aid

Under the cease-fire deal both the rebels and Assad regime forces are meant to withdraw from the Castello Road, a key supply route for the rebels, handing security control to the Russians. Rebel leaders say this would be tantamount to just handing their hard fought positions to Assad.

US Warns Russia Cease-fire Depends on Aleppo Aid

Syrian state television broadcast images appearing to show bulldozers clearing the main road into rebel held neighborhoods of Aleppo in preparation for the aid convoys.

Jens Laerke said the United Nations does not need authorization from Syria to deliver the supplies across the border, but the trucks are sitting in a “special customs zone” until it is safe.

"We know that there’s at least a quarter of a million people in eastern Aleppo who are potentially all of them in need of some kind of aid," Laerke said. "“We are as ready to go as we can possibly be...it’s highly frustrating – we know the world is watching."

The United Nations has described the cease-fire as a “critical window of opportunity” to deliver the supplies in the rebel-held eastern districts of Aleppo, but rocket fire and shelling in the area on Friday hindered the trucks' movement.

Syrian state media claim clashes between troops and rebels had broken out in Aleppo, in violation of the cease-fire. The Syrian Observatory for Human Rights reports the fighting also broke out in the Damascus neighborhood of Jobar, the home of several different rebel factions.

Meanwhile, Syria’s armed rebel factions are planning to meet Sunday to discuss whether to continue to observe the now fragile four-day-old cease-fire brokered by the United States and Russia — a truce no one consulted them about and one they fear will be exploited by Syrian President Bashar al-Assad to renew an offensive on insurgent strongholds in the besieged city of Aleppo.

The rebel observation of the cease-fire, which took effect Monday evening to coincide with the start of the major Muslim holiday of Eid al-Adha, has so far been a begrudging one and marked by distrust of American intentions toward a revolution that has left more than 400,000 people dead and half of the country’s population displaced.

There is, however, no overall unity among rebel factions about how to move ahead, although most rebel leaders contacted by VOA say they sense the cease-fire is a trap and marks a further sign of U.S. reluctance to back the revolution.

Its breakdown is inevitable, they say.

U.S. officials see the cease-fire — the second negotiated this year by Washington and Moscow over the heads of rebel militias - as a possible trigger for subsequent serious negotiations about a political transition for the war-wracked country. Rebel leaders, however, don’t believe President Assad — or his foreign backers Russia and Iran — have any wish to negotiate a political settlement and argue the weaker the insurgents become, the less likely that is to happen.

“The armed groups on the ground are still discussing what they should do about the cease-fire,” Gen. Salim Idris, former chief of the staff of the Western-backed Free Syrian Army, told VOA.

The lack of transparency in the superpower deal-making is adding, he said, to suspicion about the entire deal, making it appear murky, which is adding to rebel distrust of Western intentions toward the revolution. “I am sorry to say there isn't any trust,” he said.

On Thursday, U.S. State Department spokesman Mark Toner told reporters in Washington that the full text of the deal worked out with Russia on the truce in Syria will not be made public. “It does deal with sensitive issues that we believe, if made public, could potentially be misused,” he said.

Confusion about the deal, which among other things is meant to ground Assad’s warplanes, even appeared to wrong-foot U.S. Secretary of State John Kerry, who said on Monday that the U.S. and Russia could permit President Assad to launch new airstrikes against jihadists fighting alongside more moderate rebel factions.