By David Edwards

January 23, 2009 "Rawstory" Jan 22, 2009 --  The UN's special torture rapporteur called on the US Tuesday to pursue former president George W. Bush and defence secretary Donald Rumsfeld for torture and bad treatment of Guantanamo prisoners.

"Judicially speaking, the United States has a clear obligation" to bring proceedings against Bush and Rumsfeld, the United Nations Special Rapporteur on Torture Manfred Nowak said, in remarks to be broadcast on Germany's ZDF television Tuesday evening.

He noted Washington had ratified the UN convention on torture which required "all means, particularly penal law" to be used to bring proceedings against those violating it.

"We have all these documents that are now publicly available that prove that these methods of interrogation were intentionally ordered by Rumsfeld," against detainees at the US prison facility in Guantanamo Bay, Cuba, Nowak said.

"But obviously the highest authorities in the United States were aware of this," added Nowak, who authored a UN investigation report on the Guantanamo prison.

Bush stepped down from power Tuesday, with Barack Obama becoming the 44th president of the United States.

Asked about chances to bring legal action against Bush and Rumsfeld, Nowak said: "In principle yes. I think the evidence is on the table."

At issue, however, is whether "American law will recognise these forms of torture."

A bipartisan Senate report released last month found Rumsfeld and other top administration officials responsible for abuse of Guantanamo detainees in US custody.

It said Rumsfeld authorized harsh interrogation techniques on December 2, 2002 at the Guantanamo prison, although he ruled them out a month later.

The coercive measures were based on a document signed by Bush in February, 2002.

French, German and US rights groups have previously said they wanted to bring legal action against Rumsfeld.