IRANIAN Foreign Minister Mohammad Javad Zarif will attend talks on the Syrian civil war beginning in Vienna tomorrow after the US agreed to invite its declared enemy.

The major diplomatic breakthrough came after Washington said that it was ready to engage with Tehran if it would help resolve the protracted conflict.

US State Department spokesman John Kirby said that US officials had “always recognised that at some point in the discussion, moving toward a political transition, we have to have a conversation and a dialogue with Iran.”

Russian Foreign Minister Sergey Lavrov, US Secretary of State John Kerry and several European and Arab diplomats will also be attending the talks.

Going into the talks, the US maintains its demand that Syrian President Bashar al-Assad should be deposed as a condition of peace.

But Russia and Iran insist that Islamic Sate (Isis), the al-Qaida-affiliated Nusra Front and other terrorist groups must be defeated before a political solution can be negotiated between the legitimate government and “patriotic” opposition.

In a sign of growing cracks in the US-led coalition in the Middle East, Mr Assad met in Damascus yesterday with a delegation of French MPs led by Christian Democratic Party president Jean-Frederic Poisson.

And on Tuesday, US Defence Secretary Ashton Carter said that Washington was considering unilateral ground incursions into Syria, ostensibly against Isis.

The US has previously made land and air raids into Syria without the approval of the government.

Testifying before the Senate armed services committee, Mr Carter did not say under what circumstances the US might conduct more ground action.

“Once we locate them, no target is beyond our reach,” he said.

“We won’t hold back from supporting capable partners in opportunistic attacks against (Isis), or conducting such missions directly, whether by strikes from the air or direct action on the ground.”

But Russian parliamentary foreign affairs committee chairman Konstantin Kosachev stressed: “Any operations — air-based operations, ground-based operations — in Syria by American forces will be illegal.”

He warned that they would be trapped — “they will get involved in this ongoing conflict and the consequences will be absolutely unpredictable.”

Present at the Syria talks will be representatives from Turkey, Saudi Arabia, Jordan, the United Arab Emirates, Britain, France and Germany.