Laurent Fabius, French Minister of Foreign Affairs and International Development, at the European Parliament in Strasbourg, France, 20 January 2016. Fabius has resigned from the French government, it was reported 10 February 2016. EPA/PATRICK SEEGER

Outgoing French Foreign Minister Laurent Fabius has lashed out at his American allies over what he considers insufficient action on Syria — the latest fallout after peace talks in Geneva halted in the face of a government offensives in Aleppo and elsewhere in the country.

"There are ambiguities including among the actors of the coalition," Fabius told reporters follwing what he said would be his last ministerial conference. "I'm not going to repeat what I've said before about the main pilot of the coalition… but we don't have the feeling that there is a very strong commitment there." He didn't spell out who the "main pilot" was, but that's of course the United States.

Fabius said he was skeptical that President Obama would follow through on previous promises to back Syria's moderate opposition. "I don't think that the end of Mr. Obama's mandate will push him to act as much as his minister [secretary of state John Kerry] declares," said Fabius.

Fabius has previously criticized the US for not intervening against the regime of Bashar al-Assad after it allegedly used chemical weapons in August 2013. When Obama called off the possibility of military action, after a Russia-backed proposal to destroy Syria's chemical weapon stockpiles, Fabius said it "was not possible for us to act by ourselves."

The outgoing foreign minister's comments come days after aid workers gathered at a Syria donors conference in London said that Kerry appeared to blame the opposition for the breakdown of the Geneva talks, which were suspended out last week prior to any significant negotiations. First reported by the Middle East Eye, Kerry allegedly told the aid workers, "What do you want me to do, go to war with Russia?" when pressed on the breakdown of negotiations. In a report Tuesday in the New York Times, an aid worker said that Kerry told them in reference to the Aleppo offensive that "It's going to get much worse. This will continue for three months, and by then the opposition will be decimated."

On Monday, State Department spokesperson John Kirby didn't deny the accounts relayed by aid workers, but said that Kerry was objecting to insistence on the part of opposition representatives in Geneva that certain "preconditions" be attached to negotiations.

"If you put preconditions on it, you make it too easy, certainly for the regime and its supporters, to use that as an excuse not to talk and not to sit down and not to begin any dialogue," said Kirby.

That narrative has indeed been seized on by both the Syrian government and its Russian backers, whose air force unleashed hundreds of strikes in support of regime and allied forces as they advanced in Aleppo and other parts of the country just as peace talks were convening. According to Moscow and Damascus, opposition representatives looked for a reason to walk out of the Geneva conference, which the Aleppo offensive conveniently provided.

The city of Aleppo, which before Syria's civil war was the country's largest, is now nearly surrounded by government forces, and the UN has warned of a humanitarian catastrophe if the last opposition-controlled routes into the city are cut off. Tens of thousands of Syrians have already fled the city this month, most headed for Turkey. Officials in Ankara, however, have said Turkey, which already houses more than 2.5 million Syrian refugees, cannot accept another massive displacement.

This week, both the US and France have criticized Russia's deadly air campaign. On Tuesday, Kerry said that Russia was using banned cluster munitions in Syria to killed "women and children." At the UN, France's ambassador François Delattre has said repeatedly that the Syrian opposition was faced with the impossible task of negotiating while having a "gun to their head."

On Wednesday, Russia's ambassador to the UN Vitaly Churkin told reporters after a Security Council session on Syria that "we are not about to be apologetic," about Moscow's role in recent regime advances. He blamed members of the Council for using "humanitarian matters in order to play... a destructive role as far as the political process is concerned."

Prior to the session Delattre also spoke to reporters, saying that "the regime and its allies cannot pretend they are extending a hand to the opposition while with their other hand they are trying to destroy them."

Calling Aleppo the "martyred center of the resistance" in Syria, Delattre said it was the obligation of the government and its allies, among them the Lebanese Shia militia Hezbollah, to allow humanitarian access to the city and areas elsewhere that are under siege.

"The tangible improvement of the humanitarian situation is the condition for a credible political negotiation," said Delattre.