WASHINGTON (Reuters) - Russia has taken no “demonstrable steps” to support efforts to deliver humanitarian aid to besieged towns in Syria, even though it endorsed the effort, has aircraft in the country and has permission to use them, the U.S. State Department said on Wednesday.

People salvage goods from an aid convoy that was damaged during an airstrike in the rebel held area of al-Sakhour district of Aleppo, Syria June 4, 2016. REUTERS/Abdalrhman Ismail

State Department spokesman Mark Toner said Russian Foreign Minister Sergei Lavrov was in Vienna last month when the International Syrian Support Group called for the aerial delivery of humanitarian aid to besieged Syrians towns if full ground assess had not been granted by June 1.

That deadline passed and aerial delivery of food and medicine has not yet started, leading to criticism of the United States for lack of action.

“We are obviously disappointed, to put it mildly, that ... Russia has not taken any demonstrable steps to support the International Syria Support Group’s call for the delivery of humanitarian relief by air,” Toner said.

“They (Russians) were there in Vienna. And they committed to this deadline as well. So, you know, they can also step up and apply pressure,” he added.

Toner noted that Moscow was well-positioned to help with aid delivery.

“Russia actually has air assets on the ground in Syria and ostensibly has the permission of the Syrian government to fly,” he said.

He declined to specify whether Washington had talked to Moscow about using its aircraft to deliver aid, saying he did not want to discuss specifics. But he added, “They’re aware of our concerns.”

“They are on the ground with air assets in Syria and are able to carry out these kinds of operations,” he said.

Toner said the government of Syrian President Bashar al-Assad had prevented “full access to the delivery of humanitarian assistance” and had removed medicine and food items from some of the convoys that had been allowed.

“If the regime does not allow full supplies, we will consider it to have reneged on its commitment and (to be) continuing a policy of denying food and medicine to needy people as a military tool,” Toner said.

Asked about Assad’s pledge this week to continue fighting until he had won back “every inch” of Syrian territory, Toner said the Syrian leader was “sadly mistaken if he thinks there’s a military solution.”