Meanwhile, in a surprise statement, Central Intelligence Agency Director George Tenet took responsibility for a key error that Bush had included in his January 28 State of the Union Address to Congress, that Iraq was trying to procure nuclear material from Africa.

The critical statement in the speech that eventually raised the furor was: "The British government has learned that Saddam Hussein recently sought significant quantities of uranium from Africa."

"These 16 words should never have been included in the text written for the president," said Tenet.

"The president had every reason to believe that the text presented to him was sound."

CNN television quoted CIA sources as saying Tenet had no intention of resigning over the matter.

In an interview on US television earlier Friday, former Vermont Governor Howard Dean said current congressional investigations into whether the US government ignored CIA warnings about faulty intelligence on Iraq's weapons programs have become too politicized to be effective.

"We need a full-scale ... bipartisan investigation, outside the Congress," Dean, a leading candidate for the Democratic presidential nomination, told ABC television.

Dean said investigations currently underway in Congress are not moving forward quickly enough.

"The Republican majority is stonewalling," he said.

"We need to find out what the president knew and when he knew it," Dean added, resurrecting language used during the investigation into the Watergate political scandal, which led to the resignation of disgraced President Richard Nixon in August 1974.

"This government either is inept or simply has not told us the truth. We need to know what the answers are here," he said.

Senator Joseph Lieberman of Connecticut, another Democratic presidential hopeful, also demanded a full-scale inquiry, saying in a statement that the controversy "breaks the basic bond of trust we must have with our leaders in times of war and terrorism."

The White House has been on the defensive for several days over reports that the CIA gave the Bush administration advance warning last year that documents alleging Iraq had tried to buy enriched uranium from Niger were false.

The US president, who is on a tour of Africa, said Friday that US intelligence agencies had cleared his speech.

"I gave a speech to the nation that was cleared by intelligence services. It was a speech that detailed to the American people the dangers posed by the Saddam Hussein regime," Bush said in Uganda.

National security adviser Condoleezza Rice, traveling with the president in Africa, also said the Central Intelligence Agency had given its blessing for using the information in the address.

"If the CIA, the director of central intelligence, had said, 'Take this out of the speech,' it would have been gone, without question," she said.

Rice is one of several top Bush administration officials to insist they had no knowledge that the intelligence was fake. Earlier this week, US Defense Secretary Donald Rumsfeld said he learned that the intelligence was bad just a few days ago, while Secretary of State Colin Powell made a similar assertion on Thursday.

Senator Richard Durbin insisted on the floor of the Senate Friday that someone must have known, and called for a probe to get to the bottom of the matter.

"I can think of nothing worse than someone at the highest level of leadership ... deliberately misleading the White House, or deliberately misleading the American people about something as essential as whether nuclear weapons were being sent into Iraq before our invasion," the Illinois Democrat said.

"Who made this decision? Who decided to go forward with the statement in the president's State of the Union address which was not accurate, which was misleading?"

"That question has to be asked and answered, and it has to be done so immediately," Durbin said.

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