A humanitarian convoy reached a starved suburb of Syria's capital for the first time since 2012 on Wednesday but did not bring any food, as the opposition called for a countrywide cease-fire for the Islamic holy month of Ramadan and aid access for all Syrians.
In the north, Kurdish-led fighters aided by U.S.-led airstrikes launched a new advance on the town of Manbij, an Islamic State stronghold on a key supply route linking the Turkish border to Raqqa, the extremist group's de facto capital.
The U.N. estimates that 4,000 to 8,000 people live in the Damascus suburb of Daraya, which has been subject to a crippling government blockade since residents expelled security forces in the early stages of the 2011 uprising against President Bashar Assad.
The joint U.N., International Committee of the Red Cross, and Syrian Arab Red Crescent convoy that reached Daraya Wednesday contained medicines, vaccines, baby formula, and "nutritional items for children," the ICRC said, but no food.
"Clearly, what we brought today will not meet the needs of people in Daraya—and a one-off delivery of food will not either," Krista Armstrong of the ICRC told the AP via email, saying the organization hopes to return with food Friday. "We need to have repeated and regular access to all people living in besieged places in Syria."
It was not immediately clear why the shipment contained no food. A 36-truck aid convoy entered neighboring Moadamiyeh, which is also under government siege, at around the same time, carrying food. The suburb last received aid in February, residents said.
The U.S.- and Russia-led International Syria Support Group last month called on the U.N. to "immediately carry out a program for air bridges and air drops for all areas in need" starting June 1 if it was denied humanitarian access to designated areas, including Daraya.
The United Nations Security Council is set to meet Friday to discuss the possibility of starting humanitarian air drops to besieged areas.
Britain's ambassador to the U.N. Matthew Rycroft said the aid going to Daraya Wednesday was "too little, too late," and his country's delegation would raise the possibility of air drops at the meeting. Russian Ambassador Vitaly Churkin, however, said he believed air drops were impractical and that the land deliveries should be given a chance.
The office of the U.N. envoy to Syria said it was looking into "every possible means" to reach 592,700 people in besieged areas and millions more in hard-to-reach areas facing severe food shortages.
The opposition's High Negotiations Committee withdrew from indirect peace talks with the government last month after violence flared and the government stalled on allowing sustained humanitarian access to besieged areas and releasing detainees.
In a letter sent to the U.N. secretary-general on Wednesday, HNC chief Riad Hijab called for a "comprehensive" Ramadan cease-fire as a precondition for resuming talks in July. The holy month in which Muslims fast from dawn to dusk begins next week.
An earlier cease-fire that went into effect in late February brought relief to some opposition areas but frayed by late April.
The worsening violence has strained relations between rebel fighters and the largely-exiled HNC, and earlier this week Mohammad Alloush, who represents the powerful Islam Army in the opposition coalition, withdrew from his post as chief negotiator.
HNC official Bassma Kodmani said the armed factions would nevertheless abide by a cease-fire if the government does as well, saying the opposition group consults the rebels before making decisions.
The Syrian Democratic Forces, a Kurdish-led militia that includes Arab fighters, have meanwhile approached to within 14 kilometers (nine miles) of Manbij. The SDF announced a campaign to advance on areas around Raqqa, the de facto capital of the IS group's self-styled caliphate, last week.
"There are tens of casualties among fighters and evacuating civilians," said Nasser Haj Mansour, an adviser to the SDF. "Daesh is using its entire means to stop the forces," he told the AP by telephone from near the front line, referring to IS by its Arabic acronym.
The Britain-based Syrian Observatory for Human Rights said the fighters had recaptured at least 16 villages from IS. The monitoring group, which relies on a network of activists inside Syria, said coalition airstrikes supporting the advance have killed 15 civilians in the past 24 hours.
The Observatory said coalition aircraft struck at least one bridge between Manbij and Jarablus, a town on the Turkish border held by IS. An IS-affiliated news agency said coalition aircraft bombed all bridges between the two towns.
The SDF has also launched an offensive to capture the IS-held Tabqa air base, about 40 kilometers (25 miles) southwest of Raqqa. Mansour said the air base is a "major weapons depot" for the extremist group.
IS seized Tabqa from government forces in 2014 and massacred at least 160 captured soldiers.
Associated Press writers Jamey Keaten in Geneva and Michael Astor at the United Nations contributed to this report.
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