The paintings, which were seized in Germany after World War II, are at the centre of a long-running court battle between the US Government and a German family.

The United States, in acquiring those properties, was making quintessential public policy decisions

US Solicitor General Theodore Olson

Heirs of the late German photographer Heinrich Hoffmann insist he was the victim of wartime art pillaging, and mounted a court challenge against the US Government for taking the paintings, claiming millions of dollars in damages.

"The unique aspect of this theft is that the culprit is the United States Government," the attorney for the family, Robert White, told the Supreme Court in a filing.

War landscapes

Hitler's watercolours include street scenes and war landscapes painted before and during World War I.

American forces discovered them in 1945, not long after Hitler committed suicide, in a German castle where Hoffmann had stored them during the war.

Mr White told the Supreme Court that the seizure of the paintings and about 2.5 million photographs violated the constitutional rights of Hoffmann and his family.

The US says the art was taken "to de-Nazify Germany"

But the Bush administration urged the court to reject the appeal, arguing that the pictures Hitler painted in his early years could be categorised as art confiscated "in order to de-Nazify Germany".

The government said the works legally belong to America under a US-German treaty signed after World War II.

"The United States, in acquiring those properties, was making quintessential public policy decisions," Solicitor General Theodore Olson wrote in a filing.

Hoffmann was found guilty at the post-war Nuremberg trials of war profiteering.

Mr Olson said Hoffmann was told in 1956, a year before his death, that the only way to get his property back was through "diplomatic channels".

Profiteering

The government has been embroiled in a court battle with Hoffmann's relatives for nearly 20 years.

Texas art investor Billy F Price, who bought rights to the works, has also been involved in the dispute.

In 1993, a federal judge in Texas ordered the government to pay about $10m in damages and interest for refusing to return the art and photos. That decision was later overturned.

Mr Hoffmann and his son owned the photographs through their photography news service, Hoffmann Presse.