Washington: Despite dire US warnings and fears of a humanitarian disaster, the Trump administration has little leverage to stop Russia, Iran and the Syrian regime pressing ahead with a massive military assault against Syria’s northwest Idlib province.

Washington has threatened military action in case of a chemical weapons attack, but its mixed messaging on retaining a US presence in Syria and a cut in humanitarian aid has diminished its already limited influence over the seven-year conflict.

So the administration, which has criticised former US president Barack Obama for his inaction on Syria after the civil war started in 2011, risks appearing powerless to prevent the three nations’ plan to retake Syria’s last rebel-held area. It’s an operation that many warn will cause major bloodshed among a vulnerable population of 3 million people.

While the new US special envoy for Syria said this week that America will stay in Syria until the complete eradication of Daesh, there’s little assurance that President Donald Trump won’t again seek the withdrawal of the roughly 2,000 US troops in the country. In a sign of the administration’s shrinking commitment to Syria, it has pulled more than $200 million in stabilisation funding for liberated areas, telling other nations they should step up to pay.

A summit in Tehran on Friday between Russian President Vladimir Putin, Iranian President Hassan Rouhani and Turkish President Recep Tayyip Erdogan was seen as a chance for a diplomatic solution before a full-scale assault on Idlib. The three nations are all tacitly allied against Daesh and in support of a unified, stable Syria, but have differing views of how to achieve those ends.

After Friday’s talks, the UN envoy for Syria told the UN Security Council there were indications that the three leaders intend to continue talking to avoid a catastrophe. But above all, the summit highlighted the stark differences among these allies of convenience, with Putin and Rouhani opposing Erdogan’s call for a ceasefire.

“The Trump administration is really at a ‘hail Mary’ moment,” said Nicholas Heras, a Syria analyst and fellow at the Center for New American Security. Idlib is the last opportunity for the US to increase leverage in Syria, he said, and if the province falls before the Geneva talks, Trump administration efforts to re-engage with peace talks will likely fail.

Heras warned that the Trump team is late to formulate a coherent Syria policy. “It’s like trying to save the house as it’s burning down,” he said.