President Barack Obama is "leaning" toward a limited course of action that would "embed" the commandos with Iraqi forces, one of the defense officials, who spoke on condition of anonymity, told AFP.

A second official said the 100 troops would be capable of calling in air strikes if the administration later ordered that step.

The 100 troops would be in addition to the 275 forces that Obama has already mobilized to bolster security at the US embassy in Baghdad, the official said.

It was unclear how the White House would explain sending troops to advise the Iraqi army as Obama has vowed not to approve "boots on the ground" in Iraq -- three years after a large American force withdrew.

Obama's most senior security advisers met at the White House to discuss the potential deployment minutes before a scheduled announcement by the president on Iraq.

US military officers also confirmed that F-18 fighter jets flying from the aircraft carrier George H.W. Bush in the Persian Gulf were taking part in surveillance flights over Iraq.

The F-18 flights had taken place "over the past several days," said a military officer, who asked not to be named.

"We are flying both manned and unmanned ISR missions over Iraq," the officer said.

The Pentagon had previously acknowledged that robotic drones had been providing intelligence to the Iraqi military and that Washington had expanded the number of planes involved in recent weeks following a request from Baghdad.

NJF/NJF