Syria Aid Stuck at Border as Diplomatic Tensions Grow

UN aid trucks carrying food for besieged civilians in Aleppo remained stuck at the Syrian border Friday, as diplomatic tensions mounted between Washington and Moscow over a fragile ceasefire deal.

The truce was billed as the "last chance" to end the five-year war but it has been marred by a lack of aid deliveries, sporadic violence and friction between Russia and the United States, which brokered the deal.

On Friday a barrage of rocket fire and shelling could be heard coming from the rebel-held east Damascus district of Jobar, an AFP correspondent said.

"The Syrian army is blocking an attack by armed groups that tried to enter the capital's east via Jobar... leading to intense clashes and rocket fire," a military source told AFP.

Both the Islamist faction Faylaq al-Sham and the Fateh al-Sham Front -- formerly Al-Qaeda's Syrian affiliate -- are thought to be present in Jobar.

Syrian state television described the incident as a violation of the ceasefire.

Under the truce deal negotiated by Moscow and Washington, which took effect Monday, fighting is to halt across the country except in areas where jihadists are present.

Experts say the deal will be particularly difficult to implement in areas where Fateh al-Sham has formed strong alliances with local rebels.

The United Nations has described the ceasefire as a "critical window of opportunity" to deliver aid to rebel-held eastern districts of Aleppo city, where around 250,000 civilians are besieged by government forces.

The UN had hoped that 40 trucks of food -- enough to feed 80,000 people for one month -- could be delivered to east Aleppo as soon as possible. 

But on Friday morning, the trucks were still waiting at the border with Turkey, said David Swanson, a spokesman for the UN Office for the Coordination of Humanitarian Affairs.

"The challenge we continue to face -- and this is the very sad reality -- is ensuring all parties to the conflict, and those with influence over them, are in agreement," he told AFP. 

- 'World is watching' -Under the truce deal, the main route for humanitarian assistance into divided Aleppo, the Castello Road, would be demilitarised and aid convoys would enter from Turkey.

A military source told AFP on Friday that Syria's army "has carried out its pledge and handed over a number of points to the Russian monitoring teams" but that rebel groups had not pulled back from their positions. 

Russia on Thursday said government forces had begun to pull out from the area and accused rebel fighters of failing to withdraw as agreed.

"As humanitarians this is immensely frustrating. We're here, we're on the ground and we're ready to move... The world is watching," Swanson said. 

An AFP correspondent said Friday that no movement could be seen on the rubble-strewn Castello Road. Russian and Syrian government flags were visible in the distance on the route.

The US-Russian deal calls for the truce to be renewed every 48 hours, and for Washington and Moscow to begin unprecedented joint targeting of jihadists if it lasts a week.

Russia, a key backer of Syrian President Bashar al-Assad, accused the United States Thursday of failing to meet its obligations under the truce deal.

Russia's ambassador to the United Nations, Vitaly Churkin, said Moscow wanted a UN Security Council resolution endorsing the deal.

"We are working on it," he told reporters in New York, adding that he thought it should be adopted when the Security Council meets on Syria next Wednesday.

The United States accused Syria of blocking aid to besieged cities and warned it will not boost military cooperation with Russia unless Damascus honours the truce agreement.

"Right now, the trucks that could bring them life-saving assistance are idling on the wrong side of the border," President Barack Obama's spokesman Josh Earnest said. 

"And that's the direct responsibility of the Assad regime and their benefactors in Moscow."

Obama was due to gather top national security aids on Friday -- including his secretaries of state and defense -- with the shaky ceasefire set to dominate a meeting ostensibly about countering the Islamic State group (IS).