Powell described it yesterday as an honest mistake.
The White House acknowledged this week that the intelligence behind that information was suspect and that the charge should not have been included in the Jan. 28 address.
Some Democrats and many opponents of the war in Iraq have seized on the issue as evidence that the White House exaggerated the threat from Iraq in the run-up to the war.
Speaking at a news conference yesterday during Bush's Africa tour, Powell said that Bush's statement had been based on what appeared to be credible intelligence.
"To think that somehow we went out of our way to insert this single sentence into the State of the Union address for the purpose of deceiving and misleading the American people is an overdrawn, overblown, overwrought conclusion," Powell said.
Bush's uranium claim rested largely on documents that purported to show contacts between officials in Iraq and Niger. They were later determined to be forgeries.
U.S. intelligence analysts had decided the claim was not credible before Bush gave the January speech.
They based their conclusion largely on the negative findings of Joseph Wilson, a former U.S. ambassador in the region who traveled to Africa in February 2002 to investigate the matter on behalf of the CIA.
Accounts have differed as to who in the White House was told of this determination before Bush's speech.
Powell said that after Bush's address, additional information came to light that cast doubt on the reliability of the intelligence.
As a result, Powell said, he did not include the accusation in the presentation about the threat from Iraq that he made to the United Nations a week after Bush's address.
He said his appearance at the United Nations was to be the "definitive presentation" of the case against Saddam Hussein and "the credibility of the United States was at stake."
Asked whether that credibility was not also at stake in Bush's State of the Union address, Powell replied:
"There was sufficient evidence floating around at that time that such a statement was not totally outrageous or not to be believed or not to be appropriately used.
"It's that once we used the statement and, after further analysis and looking at other estimates we had and other information that was coming in, it turned out that the basis on which that statement was made didn't hold up."