[WASHINGTON] A bipartisan group of US senators said on Wednesday they have agreed on far-reaching sanctions to be slapped on Nato ally Turkey if its forces do not withdraw from neighbouring Syria.

Republican Senator Lindsey Graham said he and Democrat Chris Van Hollen are introducing legislation that would freeze all US assets of Turkey's political leadership, and impose sanctions on entities that do business with Turkey's military or with oil and gas companies that service its armed forces.

Mr Graham and several other US lawmakers are furious over President Donald Trump's sudden military withdrawal from positions in northern Syria, blasting the move as a betrayal of Kurdish forces who for years have helped fight Islamic militants.

"While the Administration refuses to act against Turkey, I expect strong bipartisan support" for the measure, Mr Graham said on Twitter.

AFP