Shawdesh Desk:

United States president Donald Trump imposed sanctions on Turkey on Monday and demanded the NATO ally stop a military incursion in northeast Syria that is rapidly reshaping the battlefield of the world’s deadliest ongoing war.

Trump, who gave what critics say was a de facto green light for Turkey’s assault by ordering US forces away from the conflict area, requested the ceasefire in a call with president Tayyip Erdogan.

‘The United States of America simply is not going to tolerate Turkey’s invasion in Syria any further. We are calling on Turkey to stand down, end the violence and come to the negotiating table,’ vice-president Mike Pence told reporters.

Trump also announced plans to reimpose steel tariffs on Turkey and immediately halt negotiations on a $100 billion trade deal.

‘His announcement of a package of sanctions against Turkey falls very short of reversing that humanitarian disaster,’ said US House of Representatives speaker Nancy Pelosi.

Turkey aims to neutralise the Kurdish YPG militia, the main element of Washington’s Kurdish-led ally, the Syrian Democratic Forces, which has been a key US ally in dismantling the jihadist ‘caliphate’ set up by Islamic State militants in Syria.

Ankara regards the YPG as a terrorist group aligned with Kurdish insurgents in Turkey.

Russia-backed Syrian forces on Monday took rapid advantage of the abrupt US retreat in Syria to deploy deep inside territory held by US-backed Kurdish forces south of the Turkish frontier.

Washington had announced plans for a full withdrawal from northern Syria less than 24 hours earlier.

Washington’s Kurdish former allies said they invited in the government troops as an emergency step to help fend off the Turkish assault, launched on Wednesday after what the Kurds called a US betrayal.

The Syrian army deployment is a victory for president Bashar al-Assad and his most powerful ally, Russia, giving them a foothold in the biggest remaining swath of the country that had been beyond their grasp.

They will now face Turkish armed forces along a new front line hundreds of miles long.

Syrian state media reported the army entered Manbij, a town that had been controlled by a militia allied to the Kurds. Earlier, it pushed into Tel Tamer, a town on the strategically important M4 highway that runs east-west around 30km south of the frontier with Turkey.

State television later showed residents welcoming Syrian forces into the town of Ain Issa, which lies on another part of the highway, hundreds of miles away.

US defence secretary Mark Esper said he would call on NATO allies to ‘take collective and individual’ actions against Turkey when he meets defence chiefs in Brussels next week.

Republican and Democratic leaders of the US Congress have announced plans to impose their own sanctions. Turkey’s trade with the United States is a fraction of its trade with Europe.