"I would anticipate that the major combat engagements are over because the major Iraqi units on the ground cease to show coherence," said Army Major General Stanley McChrystal, vice director of operations of the Joint Staff.

Tikrit, the hometown of deposed Iraqi President Saddam Hussein, was the last place where US forces thought they might find sizeable units of his Special Republican Guard forces, he said. But it fell Monday with only sporadic resistance.

"We will move into a phase where it will be small, albeit sharp fights," said the general.

Victoria Clarke, the Pentagon spokeswoman, told reporters not to expect a declaration of victory.

"I think you're going to see us talking for a long time about work that needs to be done, and we'll let others describe it," she said.

But a drawdown of the massive US force deployed for what turned out to be a three week war already is in the works, officials said.

Two US aircraft carriers -- the USS Kitty Hawk and the USS Constellation -- are due to head home from the Gulf as early as this week, in the first significant reduction of forces in the region, US defense officials said.

That will leave a single carrier in the Gulf, the USS Nimitz, which last week replaced the carrier USS Abraham Lincoln.

Two other carriers remain in the eastern Mediterranean -- the USS Theodore Roosvelt and the USS Harry Truman. But plans are being made to send one of those home soon, too, Vice Admiral Timothy Keating, the US naval commander, told reporters on Saturday.

F-117 stealth fighters, which opened the war March 20 with a strike aimed at killing Saddam, also were due to return from the Gulf this week to their base in New Mexico.

"Senior leaders are releasing forces from the area as the missions are completed," said Brigdier General Jim Hunt, the commander of the 49th Fighter Wing at Holloman Air Force Base in New Mexico.

General Tommy Franks, the commander of US forces in Iraq, is free to send back forces he no longer needs -- "and he is doing that," said McChrystal.

"Clearly those assets that are focused on a high intensity air campaign would be the most likely initially," he said.

"We're still early in the ground forces," he said, adding that no ground units have been redeployed so far.

The US Army's 4th Infantry Division is now almost entirely deployed inside Iraq, and other ground forces continued to flow into the region, he said.

But force requirements are under review and more military police, engineering and civil affairs units will be flowing into the country, he said.

"There will be a requirement for combat power for some period of time to maintain or to establish that secure and safe environment," McChrystal said.

"But clearly the requirement for civil affairs, for engineer organizations, military police will be significant. In fact, that's designed into the force flow," he said.

The Kitty Hawk, which arrived in the Gulf in February as part of a massive US military buildup against Iraq, will head back to its homeport in Yokosuka, Japan, the defense official said.

A cruiser, a destroyer and two support ships will go with the carrier, the official said.

The Constellation, which deployed in November as part of a scheduled rotation in the Gulf, will be going back to its homeport in San Diego, California. It has about a dozen warships in its battle groups.

SPACE.WIRE