A Red Crescent convoy prepares to leave Damascus for the besieged areas of Madaya and Zabadani during a Feb. 17, 2016, operation to deliver aid to thousands of besieged Syrians. (Louai Beshara/AFP/Getty Images)

An initial meeting between U.S. and Russian representatives tasked with organizing a cessation of hostilities in Syria will not be held until Friday, making it unlikely that an actual cease-fire will take place on that day, as originally scheduled.

The cease-fire delay came as convoys of at least 100 trucks left Damascus on Wednesday carrying U.N.-organized aid to five besieged areas of the country that have been without food or medicine.

Outside stakeholders in Syria’s civil war — including Russia and Iran in support of President Bashar al-Assad, and the United States, its partners in the region and Europe, who back the opposition — agreed early Friday in Munich on a cease-fire to “commence in one week” and humanitarian access to start immediately.

The failure to begin either initiative on time boded ill for the success of the agreement, which is supposed to lead to government-opposition peace talks. Obama administration officials have called it a last-ditch attempt to peacefully resolve the civil conflict that it maintains is undermining its separate war against the Islamic State in Syria.

Syrian Foreign Minister Walid al-Moualem, right, meets with the U.N. special envoy for Syria, Staffan de Mistura, in Damascus on Feb. 16, 2016. (SANA/Reuters)

Trucks carrying humanitarian aid were reported en route to or entering Madaya, Zabadani, and Moadamiya near Damascus, and Foua and Kefraya in Idlib province in the country’s north. The suburbs near Damascus are under siege by pro-government ­forces, while Syrian rebels have surrounded the two villages in Idlib.

Madaya gained worldwide attention in January after dozens of people died of starvation. Russia is reportedly considering airdrops of aid to the city of Deir al-Zour in the east, currently encircled by Islamic State militants.

A global advocacy group, the Syria Campaign, said Wednesday that the aid was insufficient and accused the United Nations of complicity in government sieges of civilian areas.

“The reality is the U.N. is deeply complicit in the Syrian regime’s tactic of besieging civilians,” Anna Nolan, director of the Britain-based group, said of the aid deliveries Wednesday.

“The little aid that goes in [on Wednesday] is a result of public pressure, not because of U.N. action,” she said in a statement.

Russia intervened in the civil war in the fall to prevent its ally, Assad, from being toppled by rebels. Russian airstrikes have since turned the tide against the insurgents and helped pro-regime forces­ close in on rebel strongholds in places such as Aleppo, Syria’s largest city.

The intervention has also raised tensions between NATO-member Turkey and both Russia and the United States.

Turkey, which has waged a decades-long fight against ethnic Kurdish guerrillas, has opposed U.S. support for Syrian Kurds fighting against the Islamic State. It charges­ that the Kurds are in league with Russia and Assad in attempting to take over territory north of Aleppo along the northwest Syria-Turkey border.

Since Saturday, Turkey and the Syrian Kurds have exchanged cross-border fire. The Obama administration has called for both sides to stop, leading the Turkish government to accuse Washington of a hostile attitude and support for a group that it considers terrorist.

Turkish President Recep Tayyip Erdogan said Wednesday that he has “no plans” to stop the shelling, despite U.S. entreaties.

The fighting around Aleppo has sent tens of thousands of Syrian civilians fleeing toward the closed Turkish border, where the government repeated its call for establishment of a “secure zone” inside Syria, protected by U.S. and allied forces.

German Chancellor Angela Merkel, whose country is hosting about 800,000 refugees from Syria and other countries in the region and fears an influx of even more, made a similar call Wednesday.

In an address to the German Parliament, Merkel described the situation for besieged civilians in and around Aleppo as “intolerable” and said that “nothing should be left undone” in trying to establish a no-fly zone, the international German broadcaster Deutsche Welle reported.

State Department spokesman Mark Toner said that the administration had not changed its long-standing opposition to establishment of a safe zone in northern Syria.

Toner said the administration was “pushing as fast as possible” on beginning a cease-fire, “recognizing that on both sides, there have to be consultations on the ground” before the U.S.- and Russia-led task force “can come together and meet and seriously talk about a cessation of hostilities.”

He said the U.S. team for the talks, to be held in Geneva, would be headed by Robert Malley, President Obama’s chief adviser on the Syria situation.

The administration has repeatedly rebuffed Russian entreaties to coordinate air operations in Syria, saying that Russian insistence that it is targeting the Islamic State is belied by the fact that most of its strikes have hit rebel groups fighting Assad.

But some level of coordination is necessary, Toner said, if the United States and Russia are to persuade those they are supporting on the ground to stop fighting. Among its other responsibilities, the task force is to delineate geographic areas where air attacks will cease and develop an adjudication mechanism for possible violations.

Cunningham reported from Cairo.