Brigadier General Vincent Brooks said troops were heading north from Baghdad, and pointed to the Tikrit area on a map.

Another military spokesman, Captain Frank Thorp, said members of the First Marine Division "are moving north, away from Baghdad," though he said it remained unclear when the battle for Tikrit would be waged.

"Tikrit is one of the areas where we still have concerns that there may be presence of regime forces and we have been relentless in our efforts focused at the Tikrit area, this has been ongoing for some time," said Brooks.

"We know that regime leaders have fought in and around the Tikrit area, an area where we need to physically go into to find what the conditions are," he said.

"We may find that there is not much fight left but some of the recent operations indicate that there is still some fighting to do," the general said.

He stressed that the northern city was "just one of the areas where we are concerned that there may be a presence of regime forces."

"We know there is still military equipment in the Tikrit area, further to the west and in some areas in the east. All those must be approached and investigated," he said at a news conference.

US aircraft have for days been pummelling Iraqi positions in and around Tikrit, Saddam Hussein's home base 160 kilometres (100 miles) north of Baghdad, trying to wear down the remnants of his Republican Guard.

"Only time will tell when we get into Tikrit or any of the other areas," said Captain Frank Thorp.

"The expectation from the military side is there's still fighting that will be done in the future," he said.

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