The US is withdrawing two of its three aircraft carrier groups from the Gulf as the Pentagon begins winding down its military operations in Iraq - with the third soon to follow.
US forces encountered little resistance as they entered Tikrit
The USS Kitty Hawk and USS Constellation, accompanied by their battle groups of cruisers and destroyers, are to leave the Gulf as early as this week.
And the US Air Force is withdrawing some of the land-based aircraft that opened the bombing campaign in Iraq nearly four weeks ago.
US Central Command spokesman Brigadier-General Vincent Brooks said the war in Iraq was "coming to a close" after US troops took control of the northern city of Tikrit on Monday.
The home town of ousted Iraqi leader Saddam Hussein was the last major city in the country to come under US-UK control.
Pentagon spokesman Major General Stanley McChrystal said the conflict was moving into a phase where US units could expect small, sharp fights with any remaining hostile groups.
Now though, the campaign is focusing on reconstruction and law and order, so the 1st Armoured Division will deploy from Germany with military police, engineers and civil affairs units.
And the US still has a huge force in the region. One carrier remains in the Gulf and two more are still in the eastern Mediterranean.
Last week, Britain began withdrawing some of its naval and air forces from the region, and Australia says it plans to bring its 2,000 military personnel home from Iraq soon.
No 'last stand'
Backed by helicopters and warplanes, US marines and armoured vehicles took up positions on a central square in Tikrit, which was the last Iraqi city controlled by the former regime.
The BBC's Dumeetha Luthra, in Tikrit, says that contrary to predictions there was no dramatic last stand by Iraqi forces. She says the city is quiet, with shops boarded up and streets deserted.
The troops moved into position after patchy resistance from supporters of Saddam Hussein, in which 20 Iraqis were killed.
Our correspondent says the coalition forces on the ground are now moving around the city centre, checking buildings where supporters of Saddam Hussein could be hiding, while numerous helicopters patrol the skies.
There is fighting outside the city, further to the north, an area to which it seems the loyalists have been pushed out of Tikrit, our correspondent adds.
HUMAN COST OF WAR
Iraq: At least 1254 civilian deaths*, more than 2320 military deaths**
US: 112 dead (including 27 in non-combat accidents, 6 to 'friendly fire', 2 under investigation), 2 missing
UK: 30 dead (including 16 in non-combat accidents, 5 to 'friendly fire')
Media: 12 dead, 2 missing
*Former regime, **US military
Order is gradually being restored to cities including the capital Baghdad after days of looting following the collapse of Saddam Hussein's regime. US-Iraqi joint patrols began work in Baghdad on Monday.
More than 2,000 Iraqi policemen are reported to have answered a US call for officers from the old regime to return to work.
US troops accompanied Iraqi squad cars in the capital, while order was also restored in the northern cities of Kirkuk and Mosul, which fell to Kurdish fighters in the last few days.
"We're beginning to see a downward trend in looting," Central Command spokesman Captain Frank Thorp said.