About 15,000 US soldiers and reservists have been told to prepare for service in Iraq , as other countries hold back from pledging troops.
Many troops will be given the chance to have a 15-day break
The announcement follows earlier statements by senior US officers this week, that National Guard and Reserve troops would be needed.
Other countries failed to respond to President George W Bush's plea for help for help in stabilising the country.
US troops come under almost daily attack.
On Saturday, a hotel near a media centre used by US troops in Baghdad was targeted in a rocket-propelled grenade attack.
The attack on the prestigious al-Rashid hotel took place at about 0630 (0230 GMT) and caused superficial damage but no casualties.
But 80 US soldiers have been killed by guerrillas since
President George W Bush declared major combat over on 1 May.
The first US troops to get a 15-day holiday - in a bid to boost morale among the ranks - have arrived back home on their break.
Just under 200 soldiers were flown out of Iraq and thousands more could be eligible to take a sought-after respite.
The BBC's Pentagon correspondent Nick Childs said the recuperation programme shows how concerned military commanders are about the morale of their forces.
"Troops' families and reservist associations are suggesting that the scale and duration of this mobilisation is hitting both morale and recruitment," says our correspondent.
On Friday 10,000 Army National Guard troops were activated and 5,000 more Army Guard soldiers were put on alert for likely service in Iraq.
Military commanders are concerned at the morale among US soldiers
There are currently two other multinational divisions in
Iraq headed by Britain and Poland.
The United States is pressing for volunteers to form a third multinational division, but so far they have not come forward.
US Army General John Abizaid, head of the US Central
Command and commander of the US military operation in Iraq, said he could not rule out calling up additional troops.
Marine Corps General Peter Pace, vice chairman of the Joint Chiefs of Staff and the nation's second-ranking officer told reporters: "There are many countries out there talking about it
(contributing troops), and we have every hope that that will happen.
"But hope is not a plan."