Beirut: The United States warned it would take “firm and appropriate measures” to protect a ceasefire in southern Syria if Bashar Al Assad’s forces move against rebels there.

The area in southwestern Syria, between the border city of Daraa and the Israeli-occupied Golan Heights, has emerged as a flashpoint in a wider standoff between regional arch-rivals Israel and Iran.

The US, Russia, and Jordan agreed last year to include Dara’a in a “de-escalation zone” to freeze the lines of conflict. But regime forces have recently dropped leaflets on rebel-held areas warning of an imminent offensive and urging fighters to lay down their arms, Syrian regime media said on Friday.

In a statement released on Friday, the US State Department said it was concerned by reports that Al Assad’s forces were preparing for an operation in southwestern Syria. It warned the regime against “any actions that risk broadening the conflict.”

Al Assad has relied on Russia, Iran and the Lebanese militant group Hezbollah to battle an uprising against his family’s decades-long rule and rollback a Daesh insurgency that grew out of the country’s seven-year civil war. Iran has sent military commanders to oversee battles and organise militias from across the Middle East to fight alongside Al Assad’s troops.

The US and Israel view Iran’s extensive military presence in Syria as a threat to Israel and have threatened action. The Israeli regime is believed to be behind dozens of air strikes in recent years against Hezbollah, Iran, and Syrian regime military positions.

Earlier this month, Israel bombed Iranian military positions in Syria in what it said was retaliation for an Iranian rocket attack on the occupied Golan Heights. Israel called it its most serious operation in Syria since the 1973 Mideast war.

The regime began moving reinforcements to Daraa province this week after expelling the last rebels and Daesh terrorists from around Damascus, according to the Britain-based Syrian Observatory for Human Rights, which closely monitors the war.

Leaflets dropped on northern Dara’a, which is divided between rebel and regime-controlled areas, warned: “The men of the Syrian army are coming.”

The Syrian uprising began in Dara’a in 2011. The ceasefire has slowly disintegrated as regime warplanes have carried out air strikes against rebel-held areas.