Syria's foreign minister said Thursday Western aggression would not prevent Damascus from retaking all Syrian territory, amid fears of an imminent government offensive against the rebel-held province of Idlib.

"A tripartite aggression or not, it will not influence our determination to liberate the entire Syrian territory," Walid Muallem said in Moscow after talks with his Russian counterpart Sergei Lavrov, referring to Washington, Paris and London.

Government forces have been massing around Idlib -- Syria's only remaining rebel-held province -- for days and looked poised to launch what could be the last major battle of the civil war that has torn the country apart since 2011.

Last week, the United States, France and Britain threatened to respond if Syrian President Bashar al-Assad uses chemical weapons in its offensive to retake Idlib province.

Muallem said that the government's main target was fighters belonging to Al Nusra Front jihadists.

"The Syrian command has taken a decision to defeat Al-Nusra Front in Idlib no matter the sacrifices that it would entail," Muallem said in Arabic, referring to the former Syrian affiliate of Al-Qaeda.

He insisted however that the authorities wanted to win back territory through reconciliation agreements.

"We are ready to make every effort to avoid victims among the civilians," he added.

On Thursday, key brokers held last-ditch talks on the fate of Idlib, hoping to stave off a government offensive the UN has warned could spark catastrophe.