The United Nations is still waiting for Syrian government agreement for an aid convoy to enter the besieged town of Daraya and has requested approval to airlift food into four locations if land routes are unavailable, U.N. officials said on Tuesday.

Rebel-held Daraya got its first U.N. aid convoy since 2012 on June 1, but the shipment did not include food. The United Nations has said malnourished children in the Damascus suburb will die without outside help, a claim President Bashar al-Assad's government has denied.

"The blockage of aid is a political issue," U.N. spokesman Ahmad Fawzi told a regular U.N. briefing in Geneva. "Daraya is 12 km (7.5 miles) from Damascus, so it can be done but we need the political go-ahead from the government."

Daraya is one of four besieged areas for which the U.N. presented the Syrian foreign ministry on Sunday a backup plan to airlift food if land access is not approved, U.N. spokesman Stephane Dujarric told reporters in New York. It is awaiting approval.

"The written request included a plan for airlifts – not airdrops - as a last resort, to Daraya, Douma and Mouadamiya in rural Damascus Governorate, and Al Waer in Homs Governorate," Dujarric said.

So far Damascus has only authorized the delivery of medical assistance, school supplies and children's milk to Douma, Daraya and Mouadamiya during June, not food.

Al Waer was not among the areas approved for June. The Syrian government noted in a statement that the Syrian Arab Red Crescent had delivered seven trucks of medical supplies, food and children's milk to the area on June 1.

The U.N. convoy got through to Daraya on the day the Syrian government faced a deadline to admit aid by road or risk having air drops imposed by the countries of the International Syria Support Group (ISSG), which includes Syria's ally Russia.

The convoy brought baby milk and medical supplies to support an estimated 4,000 civilians in the town besieged by government forces. U.N. officials had hoped food would arrive in a second convoy on Friday, but that was delayed with no government approval.

Syria's opposition said the government approved the first convoy in a cynical ploy to alleviate international pressure.

Bouthaina Shaaban, an adviser to Assad, said last week that "nobody is starving in Daraya", which was "producing peas and beans and food and wild berries that is enough for the entire Syria."