"A contingency plan has been prepared at my request by the defence minister to prepare for a possible request (to send troops)," he told reporters following talks with his visiting Swedish counterpart Goeran Persson.

"There has been no concrete request, no decision has been taken in this direction. What there is is a study of the situation and an analysis of the possibilities," Durao Barroso added. "We have done our homework."

A vocal supporter of the US-led invasion of Iraq, centre-right Durao Barroso nonetheless ruled out contributing Portuguese troops to combat roles in the military campaign.

Earlier Portuguese President Jorge Sampaio said he hoped the United Nations could quickly move into war-torn Iraq and help rebuild the country.

"I hope the United Nations are able (to move into Iraq) because it is becoming more and more urgent that they assume their role," he told reporters on the sidelines of a conference on human rights.

"It is not possible to continue seeing the suffering, the confusion, the complete undoing of everything," he added in a reference to the widespread looting which has hit Iraq since the fall of Saddam Hussein's regime on Wednesday.

"It is a great challenge (for the United Nations), I think those who participated in this war should understand that," he said.

Russia, France and Germany -- the main opponents to the US-led war -- have been arguing for the United Nations to play a central role in reconstructing Iraq.

The United States has insisted its military forces must remain in control in the immediate administration of post-war Iraq, but said the United Nations had "a vital role" to play in bringing stability and prosperity to the war-ravaged country.

SPACE.WIRE