In Mosul, "we have indications that several forces are chosing not to fight and are going south out of the city," said Navy Ensign David Luckett, a spokesman at the US Central Command (Centcom)'s war headquarters in Qatar.

He did not confirm reports that Iraqi officers were negotiating a surrender to US troops who have entered the city, but said US forces were "talking to people from the Iraqi government and the Iraqi army at all levels" in Iraq.

"We are optimistic the people of Iraq will live freely as they choose, in the near future," he said when asked whether he expected the city to fall soon.

In Kirkuk, he said, "we have forces within the city working to instill a secure atmosphere."

Kurdish fighters captured the city with the support of US forces.

"There is still a lot of uncertainty. There is still a lot of hard work to be done, we anticipate sporadic resistance," Luckett said, pointing out this was also the case in other areas.

US-led forces also continued bombing Tikrit, the northern hometown and stronghold of Iraqi President Saddam Hussein, the spokesman said.

"We continue to shape the battle space," he said, explaining that this meant preparing the ground for "a successful mission" involving minimal loss of life.

US military officials say there are few ground troops around Tikrit at this stage, and that operations are focused largely on airstrikes against military and government targets in the area.

US military officials say there are several command and control facilities in Tikrit, a city seen as a symbol of Saddam's 24-year rule.

Saddam was born in a community near Tikrit, 170 kilometers (105 miles) north of Baghdad, and the region is considered his principal power base.

SPACE.WIRE