The top-ranking officer in the American military said yesterday the United States is actively considering the direct use of troops in the toughest forthcoming fights against the Islamic State (IS) in Iraq, less than a week after President Barack Obama doubled troop levels there .

Gen Martin Dempsey, chairman of the joint chiefs of staff, indicated to the House of Representatives armed services committee that the strength of IS relative to the Iraqi army may be such that he would recommend abandoning Mr Obama's oft-repeated pledge against returning US ground troops to combat in Iraq.

Retaking the critical city of Mosul, Iraq's second largest, and re-establishing the border between Iraq and Syria that IS has erased "will be fairly complex terrain" for the Iraqi security forces that the US is once again supporting, Gen Dempsey acknowledged.