The US plans to keep troops in northern Syria indefinitely to prevent the resurgence of the Islamic State of Iraq and the Levant (Isil) and counter the influence of Iran, Rex Tillerson, the US secretary of state, has said.

Laying out the Trump administration’s broad strategy for Syria, Mr Tillerson said a quick withdrawal from Syria would give the jihadist group space to regroup after years of defeat on the battlefield.

“The United States will maintain a military presence in Syria focused on ensuring Isil cannot re-emerge,” he said. “We cannot make the same mistakes that were made in 2011 when a premature departure from Iraq allowed al-Qaeda in Iraq to survive and eventually morph into Isil”.

Mr Tillerson said the US remained committed to seeing Bashar al-Assad, the Syrian leader, step down from power and would refuse to normalise diplomatic relations with Syria or provide reconstruction funds as “tools of pressure” to get Assad to go.

But America’s top diplomat also called for “patience in the departure of Assad and the establishment of new leadership”, a signal that the US does not expect the Syrian leader, who has survived nearly seven years of civil war, to relinquish power any time soon.