In addition, Secretary of State Colin Powell said Washington was working with the United Nations, the European Union and Interpol to prevent stolen objects from leaving Iraq and warned thieves that they would face prosecution.

"This kind of looting causes irretrievable loss to the understanding of history and to the efforts of Iraqi and international scholars to study and gain new insight into our past," Powell said in a statement.

"Objects and documents taken from the museums and sites are the property of the Iraqi nation, and under Iraqi law they are therefore stolen property, whether found in Iraq or in other nations," he said.

"Anyone knowingly possessing or dealing in such objects is committing a crime," Powell said, adding a specific warning for US citizens not to traffic in such items.

Earlier, Powell told reporters that the United States was deeply concerned by the looting of the national museum in Baghdad, which he called "one of the great museums in the world."

"The United States understands its obligations and will be taking a leading role with respect to antiquities in general, but this museum in particular," he said.

Powell said Washington would work with others "not only secure the facility, but to recover that which has been taken and also to participate in restoring that which has been broken."

Deputy State Department spokesman Philip Reeker said US officials had been in contact with the international police agency Interpol to locate and return stolen objects before they turned up in the thriving global black market for such items.

Powell said he had spoken Monday with Greek Foreign Minister George Papandreou, whose country holds the rotating presidency of the European Union, about possible ways to protect Iraq's cultural heritage.

And, he said US officials had been in touch with the United Nations Educational Scientific and Cultural Organization (UNESCO) to explore steps that could be taken.

UNESCO's chief, Koichiro Matsuura, on Saturday called on US and British authorities to immediately protect Iraq's cultural heritage by monitoring and guarding archeological sites and cultural institutions.

The museums in Baghdad and in the northern city of Mosul should be guarded by the military, Matsuura said, according to a UNESCO statement released in Paris.

The organization also said it had contacted Iraq's neighbors to stop any "illegal export of Iraqi cultural goods."

Iraq's national museum fell victim to looters on Friday in the lawless atmosphere that engulfed Baghdad after the arrival there of US troops on Wednesday.

Pottery artifacts and statues were broken and overturned, while administrative offices were wrecked, according to witnesses.

Iraq, among the earliest cradles of civilization and home to the remains of such ancient Mesopotamian cities as Babylon, Ur and Nineveh, has one of the richest archaeological heritages in the world.

Shortly after the war began on March 20, a group of 18 prominent archaeologists appealed for the US-led coalition to spare Iraq's priceless antiquities.

"The extraordinary significance of the monuments, museums and archeological sites of Iraq -- ancient Mesopotamia -- imposes an obligation on all peoples and governments to protect them," they said in March 21 open letter published in Science magazine.

They also called on the international community to take a post-war role in assisting in the protection of antiquities from looting and themselves pledged to help Iraqi Department of Antiquities do its job.

Some of the signatories were among a team of scholars to have worked with the Pentagon and the State Department before the war to identify some 4,000 sites that should be protected.

Despite these efforts, they expressed deep concern that the fall of the Iraqi leader Saddam Hussein would erode the control of cultural watchdogs in the country and spur looting, particularly at the museums in Baghdad and Mosul.

SPACE.WIRE