US special forces teams were already behind the lines inside Syria attempting to kill foreign Islamic extremists before they cross the border with Iraq, the newspaper said.

Citing unnamed sources familiar with the operations, it reported that a group focused on the "neutralisation" of Iraqi guerrilla leaders was being set up.

"This is basically an assassination programme. That is what is being conceptualised here. This is a hunter-killer team," a former senior US intelligence official told the paper.

He added that he feared the new tactics and enhanced cooperation with Israel would inflame a volatile situation in the Middle East.

The Guardian said that according to US intelligence and military sources, the Israeli Defence Force had sent urban warfare specialists to Fort Bragg in North Carolina, the home of US special forces.

According to two sources, Israeli military "consultants" had also visited Iraq, the paper reported.

WAR.WIRE