In the center, more than 10,000 Iraqis gathered by the graveside of slain Shiite Ayatollah Mohammad Baqer al-Hakim to mark the end of the official mourning period for the influential cleric, killed along with 82 others in a car bombing on August 29.

As Iraqis grieved for Hakim, Lieutenant General Ricardo Sanchez warned his troops were facing a deadlier foe on the ground than a half-year ago when US forces toppled Saddam Hussein's authoritarian regime.

"The enemy has evolved and he is a little more lethal, a little more complex, a little more sophisticated and in some cases a little more tenacious," Sanchez told reporters Thursday.

The danger of the enemy "has increased a little bit because they are using more improvised explosives against us ... So he has evolved, he is learning, but so are we and this will continue for a little while," Sanchez said.

He noted every week three-to-six soldiers were dying and another 40 were wounded.

Sanchez remarked the resistance had expanded from just pro-Saddam loyalists to a steady flow of foreign "terrorists" slipping into Iraq from Syria and northern Iran.

The commander warned his soldiers would not be exiting the country anytime soon.

"It will definitely be years. We never said it would be anything less than years," Sanchez said about the moment when US forces will leave the country.

Meanwhile, the main Iraqi Shiite Muslim group on Friday criticised Washington's draft UN Security Council resolution because it does not set a deadline for a withdrawal of coalition forces, Egyptian state media reported.

Reda Jawad Taqi, a representative of the Supreme Council for the Islamic Revolution in Iraq (SCIRI), said the draft was "weak" because it does not include "a deadline and a timetable for the withdrawal of coalition forces," MENA news agency reported.