President Donald Trump has approved a mission for US troops to return to Syria to "secure" its oil fields, despite promises to withdraw all forces from the war-torn country.

Under Mr Trump’s new plan, troops would protect a large swath of land controlled by Syrian Kurdish fighters that stretches nearly 90 miles of the oil-rich province of Deir Ezzor in the east.

The Pentagon will not say how many of the some 2,000 forces it once had in Syria would remain, however officials have suggested the total number could reach as many as 800.

A small contingent was pictured last week patrolling the wells in Deir Ezzor.

Mr Trump had announced the US was withdrawing all troops early last month, paving the way for a Turkish offensive on Kurdish forces in north-east Syria.