PARIS/MOSCOW/BEIRUT (Reuters) - France is to launch a new push for United Nations backing for a ceasefire in Syria that would allow aid into the city of Aleppo after some of the heaviest bombing of the war.

The sun sets over Aleppo as seen from rebel-held part of the city, Syria October 5, 2016. To match Insight MIDEAST-CRISIS/SYRIA-ALEPPO REUTERS/Abdalrhman Ismail TPX IMAGES OF THE DAY

As diplomatic efforts resumed, the Syrian military said army commanders had decided to scale back air strikes and shelling in Aleppo to alleviate the humanitarian situation there.

It said civilians in rebel-held eastern Aleppo were being used as human shields and a reduced level of bombardment would allow people to leave for safer areas.

Intense Syrian and Russian bombing of rebel-held areas of the northern city of Aleppo followed the collapse last month of a ceasefire brokered by Moscow and Washington, which backs some rebel groups. The United States broke off talks with Russia on Monday, accusing it of breaking its commitments.

France said Foreign Minister Jean-Marc Ayrault would travel to Russia and the United States on Thursday and Friday to try to persuade both sides to adopt a Security Council resolution to impose a new truce.

Ayrault has accused Syria, backed by Russia and Iran, of war crimes as part of an “all-out war” on its people. Damascus rejects the accusation, saying it is only fighting terrorists.

Speaking to French television channel LCI, Ayrault said: “If you’re complicit in war crimes then one day you will be held accountable, including legally. I think with the Russians you have to speak the truth and not try to please them.”

The former prime minister said he would also ask Washington to be “more efficient and engaged” and not allow a laissez-faire attitude to take over just because presidential elections were approaching in November.

“ALL THAT’S LEFT”

Russian Foreign Minister Sergei Lavrov and U.S. Secretary of State John Kerry discussed Syria by telephone on Wednesday, but no details emerged. The Russian Foreign Ministry confirmed that Lavrov would meet Ayrault in Moscow on Thursday.

The two-week-old Russian-backed Syrian government offensive aims to capture eastern Aleppo and crush the last urban stronghold of a revolt against Syrian President Bashar al-Assad that began in 2011.

Half of the estimated 275,000 Syrians besieged in the rebel-held eastern part of the city want to leave, the United Nations said, with food supplies running short and people driven to burning plastic for fuel.

Mothers were reportedly tying ropes around their stomachs or drinking large amounts of water to reduce the feeling of hunger and prioritise food for their children, the U.N. Office for Coordination of Humanitarian Affairs said in Geneva.

The Security Council began negotiations on Monday on a French and Spanish draft resolution that urges Russia and the United States to ensure an immediate truce in Aleppo and to “put an end to all military flights over the city”.

“This trip is in the framework of efforts by France to get a resolution adopted at the U.N. Security Council opening the path for a ceasefire in Aleppo and aid access for populations that need it so much,” the French foreign ministry said.

Russian U.N. Ambassador Vitaly Churkin said on Monday that Moscow was engaged in discussions on the draft text even if he was not especially enthusiastic about its language.

The draft text, seen by Reuters, urges Russia and the United States “to ensure the immediate implementation of the cessation of hostilities, starting with Aleppo, and, to that effect, to put an end to all military flights over the city.”

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The draft also asks U.N. chief Ban Ki-moon to propose options for U.N.-supervised monitoring of a truce and threatens to “take further measures” in the event of non-compliance by “any party to the Syrian domestic conflict”.

A senior Security Council diplomat, speaking on condition of anonymity, said: “In the experts’ negotiations they (Russia) have opposed every single dot and comma of the resolution.”

French officials have said that if Moscow were to oppose the resolution they would be ready to put it forward anyway to force Moscow into a veto, underscoring its complicity with the Syrian government.

“It’s all that’s left,” said a French diplomatic source. “We’re not fools. The Russians aren’t going to begin respecting human rights from one day to the next, but it’s all we have to put pressure on them.”

GULF STATES

Ayrault said in the television interview that the situation was unacceptable. “It is deeply shocking and shameful,” he said. “France will not close its eyes and do nothing. It’s cynicism that fools nobody.”

The collapse of the latest Syria ceasefire has heightened the possibility that Gulf states including Saudi Arabia and Qatar - backers of Syrian rebels - might arm the opposition with shoulder-fired missiles to defend themselves against Syrian and Russian warplanes, U.S. officials have said.

Qatar’s foreign minister said outside powers need to act fast to protect Syrians because foreign military backing for the government is “changing the equation” of the war.

A United Nations expert said that analysis of satellite imagery of a deadly and disputed attack on an aid convoy in Syria last month showed that it was an air strike.

Some 20 people were killed in the attack on the U.N. and Syrian Arab Red Crescent convoy at Urem Al-Kubra near Aleppo.

The United States blamed two Russian warplanes which it said were in the skies above the area at the time of the incident. Moscow denies this and says the convoy caught fire.

“With our analysis we determined it was an air strike and I think multiple other sources have said that as well,” Lars Bromley, research adviser at UNOSAT, told a news briefing.

In northern Syria, rebels were expecting stiff resistance from Islamic State in their attempt to capture a village that is of great symbolic significance to the jihadists, a rebel commander said.

With Turkish backing, rebels fighting under the Free Syrian Army banner have advanced to within a few kilometres (miles) of Dabiq, the site of an apocalyptic prophecy central to the militant group’s ideology.