US forces will target Syrian anti-aircraft systems if they take aim at American planes conducting strikes inside Syria against Islamic State rebels.

Speaking on condition of anonymity, a senior official said that Washington had a good sense of where hostile Syrian batteries were located and US pilots would be tasked with rules of engagement that would allow them to protect themselves.

Last week, President Barack Obama announced that he would expand air strikes against IS in Iraq and was prepared to strike at the militant group in Syria.

In response, Syrian National Reconciliation Minister Ali Haidar said that any action against the jihadist group on Syrian territory without the consent of the Damascus government would be viewed as an attack on Syria.

The senior US official said that Syrian President Bashar al-Assad would have a choice to make in the event of US strikes against IS.

If Assad used military capabilities to interfere with the US capacity to strike at IS in Syria, he would put units involved in such action at risk, the official said.

Obama has ruled out the idea that his government could co-operate with Assad’s forces to go after a common enemy in the Islamic State, which has overrun large areas of northern Iraq and Syria.

The US government sees Assad as tantamount to a war criminal who has turned the horror of civil war on his own people. Washington has consistently said that he should leave power.