In a related development, the State Department said it obtained documents purporting to back the Africa claim which turned out to be forgeries three months before the president's speech, but did not turn them over to U.N. inspectors.
Meanwhile, a second prewar claim in President Bush's State of the Union address is coming under new scrutiny. Two weapons experts say a key Iraqi scientist has told the CIA that high-strength aluminum tubes bought by Baghdad were not intended for nuclear weapons production, as the president had suggested.
Mahdi Shukur Obeidi, the scientist who made headlines last month when he surrendered documents and weapons-making parts that he had buried in his Baghdad backyard, has also told the CIA that Iraq hadn't rebuilt its nuclear weapons program since the first Gulf War of 1991.
Elsewhere, a body found in central England matches the description of a missing Ministry of Defense adviser who had become embroiled in a controversy over the government's intelligence dossiers on Iraqi arms, police said Friday. David Kelly appeared before a Parliamentary committee earlier this week to face questions over a British Broadcasting Corp. report, that government aides doctored intelligence on Iraqi weapons to strengthen the case for war.
The new details about the back-and-forth between the CIA and the White House over the president's Jan. 28 address emerged as Democrats pressed for more background on how the Africa allegation made it into the speech.
In his State of the Union, Mr. Bush said: "The British government has learned that Saddam Hussein recently sought significant quantities of uranium from Africa."
The White House last week withdrew the claim because it was based on shaky intelligence.
Documents purported to be evidence of an Iraqi attempt to buy uranium from Niger turned out to be forgeries, and two U.S. officials who checked out the allegations in early 2002 could not prove them.
The CIA had other evidence that Iraq sought uranium in Congo and Somalia, but it was not solid. The agency tried to prevent Britain from mentioning the Africa allegation in a September dossier about Iraq's alleged weapons, and blocked a specific reference to the Niger claim from a speech by the president in October.
Last week, CIA director George Tenet accepted responsibility for the reference to the unsubstantiated claim.
Intelligence sources say it was the president's National Security Council that was pressing the issue, reports CBS News Chief White House Correspondent John Roberts.
According to testimony by CIA analyst Alan Foley at Wednesday's closed-door session of the Senate Intelligence Committee, NSC official Robert Joseph wanted to use specific intelligence on Niger in the speech.
Officials say Foley testified that he warned Joseph that the CIA had doubts and suggested the claim be left out. Joseph then asked if the speech could refer to a British report that referenced the allegation.
Foley testified he again warned Johnson the CIA had doubts about the British claim.
Foley said he did finally agree it would be technically correct if the NSC laid the claim off on the British. According to The New York Times, Foley did not allege he felt pressure from the White House.
"In the end, he agreed with the NSC official's formulation that it would be technically accurate to say the British had said what they had said," the U.S. official said.
Tenet, though, was not made aware of the discussion. He has said he never reviewed the speech.
Previously, the White House has said the CIA objected only to the way the Africa claim was made. National security adviser Condoleeza Rice told reporters last week that "some specifics about amount and place were taken out," and the CIA "cleared the speech."
Until now, the administration has said it only received the forged documents after the president's speech. But State Department spokesman Richard Boucher said Thursday they were obtained in October and shared with the CIA.
The U.S. suspected an attempted Niger deal before those documents arrived, and dispatched an envoy, Joseph Wilson, who found nothing solid to substantiate the claim.
It was unclear why the documents were not handed to U.N. inspectors earlier. The International Atomic Energy Agency quickly deemed the papers forgeries after receiving them from the United States. According to an Italian newspaper that claims to have seen the documents, they included obvious frauds, including a letter both addressed to and signed by the president of Niger.
Democrats have cited questions about the uranium intelligence as showing the need for a broad investigation into prewar intelligence, beyond the inquiries under way by the House and Senate intelligence Committees.
Despite claims that Iraq had material for making chemical and biological weapons and was restarting its nuclear program, no weapons have yet been found.
The Bush administration has claimed that the Africa claim was a small part of their case for war. Neither the administration nor Blair ever referred to Niger by name.
Mr. Bush didn't respond directly when asked Thursday whether he took responsibility for the now-discredited statement, saying, "I take responsibility for putting troops into action. I take responsibility for making the tough decision to put together a coalition to remove Saddam Hussein."
The president added that American and British intelligence "made a clear and compelling case that Saddam Hussein was a threat to security and peace."
"I strongly believe he was trying to reconstitute his nuclear weapons program," Mr. Bush said, adding that after the first Persian Gulf War in 1991, "it became clear that Saddam Hussein was much closer to developing nuclear weapons than anybody ever imagined."
The British stand by their Africa claim, saying they had evidence other than the forged documents.