In January 2003, the president used his State of the Union speech to argue for war on Iraq. He said: "The British government has learned that Saddam Hussein recently sought significant quantities of uranium from Africa."

Those allegations has turned out to be false, and now the president is facing one of his biggest political challenges since the war on terror began.

ABCNEWS has assembled a timeline to help readers understand how the false information made it into one of the president's most important speeches.

February 2002
The CIA dispatches Ambassador Joseph C. Wilson to Niger to investigate claim of attempted uranium sale to Iraq, reportedly in response to questions from aides in Vice President Dick Cheney's office. Wilson spends eight days in Niger and concludes the allegations are "bogus and unrealistic." Wilson later says he reported this verbally to the CIA in a debriefing upon his return.

March 9, 2002
CIA reportedly sends cable that does not name Wilson but says Nigerien officials denied the allegations.

September 2002
The story that Iraq purchased uranium from Niger is published in a British dossier. The CIA "tried unsuccessfully … to persuade the British government to drop [the references]," according to a July 12, 2003, Washington Post report.

Late September 2002
CIA Director George Tenet and top aides make two presentations on Capitol Hill. They reportedly are asked about uranium purchase story. They say there was info that Iraq had attempted to buy uranium but there were doubts about its credibility. Tenet did not tell lawmakers that an envoy had been sent to Niger, according to a July 12, 2003, Washington Post report.

October 2002
The National Intelligence Estimate is produced. It says "a foreign government service reported that as of early 2001, Niger planned to send several tons of pure uranium (probably yellowcake) to Iraq," according to a July 11, 2003, statement from Tenet. It also states: "We do not know the status of this arrangement." Much later in the text, State Department researchers call the allegations "highly dubious."

October 2002
The CIA releases a White Paper document that omits the uranium allegations.

Oct. 7, 2002
The president gives a speech on Iraq in Cincinnati. He does not refer to the uranium story at the urging of the CIA, according to a July 2003 Washington Post report.

Dec. 12, 2002
American intelligence agencies say Iraq's 12,000-page weapons declaration to the United Nations doesn't account for chemical and biological agents that were missing at the end of the Gulf War.

Dec. 19, 2002
The State Department says in a fact sheet that Iraq omitted its attempts to purchase uranium from Niger in its report to United Nations on its weapons program.

Jan. 23, 2003
National Security Adviser Condoleezza Rice publishes a piece in New York Times, "Why We Know Iraq Is Lying," and says that the declaration of weapons "fails to account for or explain Iraq's efforts to get uranium from abroad."

Jan. 23, 2003
At the Council on Foreign Relations, Deputy Defense Secretary Paul Wolfowitz also faults the Iraqi report, saying "there is no mention of Iraqi efforts to procure uranium from abroad."

Jan. 28, 2003
The president gives his State of the Union address. He says: "The British government has learned that Saddam Hussein recently sought significant quantities of uranium from Africa."

Jan. 29, 2003
At Pentagon briefing, Defense Secretary Donald Rumsfeld says Saddam Hussein "recently was discovered seeking significant quantities of uranium from Africa."

Feb. 5, 2003
Secretary of State Colin Powell makes his presentation to the United Nations. He omits the uranium story. Three months later, he tells reporters he did not repeat the allegation because "I didn't sense in going through it all that I saw enough substantiation of it that would meet the tests that we were applying."

March 7, 2003
International Atomic Energy Agency head Mohamed ElBaradei says "the reports of recent uranium transaction between Iraq and Niger are in fact not authentic" and "unfounded."

March 16, 2003
On NBC's Meet the Press, Vice President Cheney says: "I think Mr. ElBaradei, frankly, is wrong."

March 20, 2003
President Bush announces the start of the military campaign against Iraq.

May 2, 2003
President Bush declares the end of major combat operations in Iraq.

May 30, 2003
In response to growing criticism of U.S. pre-war intelligence, CIA Director George Tenet releases a statement defending the agency's findings. He writes, "The integrity of our process was maintained throughout and any suggestion to the contrary is simply wrong."

June 8, 2003
On ABCNEWS' This Week, Rice says that at the time the State of the Union address was being prepared, "there were also other sources that said that … the Iraqis were seeking yellowcake, uranium oxide from Africa. And that was taken out of a British report. Clearly, that particular report, we learned subsequently, subsequently, was not credible."

June 12, 2003
The Washington Post quotes a White House spokesman acknowledging documents "detailing a transaction between Iraq and Niger were forged." However, the spokesman says they were "only one piece of evidence in a larger body of evidence suggesting Iraq attempted to purchase uranium from Africa."

July 6, 2003
Ambassador Wilson publishes an op-ed in the New York Times, for the first time identifying himself as the Niger envoy. Wilson writes: "Based on my experience with the administration in the months leading up to the war, I have little choice but to conclude that some of the intelligence related to Iraq's nuclear weapons program was twisted to exaggerate the Iraqi threat."

July 9, 2003
White House press secretary Ari Fleischer tells reporters, "With the advantage of hindsight, it's known now what was not known by the White House prior to the speech. This information should not have risen to the level of a presidential speech."

July 9, 2003
In testimony before Senate Armed Services Committee, Rumsfeld says it was only "within recent days" that he learned that reports about uranium coming out of Africa were bogus.

July 11, 2003
The president says, "I gave a speech to the nation that was cleared by the intelligence services."

July 11, 2003
Rice tells reporters the CIA cleared the State of the Union speech "in its entirety."

July 11, 2003
Tenet releases a statement saying the CIA approved of the State of the Union speech before it was delivered. Tenet says, "These 16 words should never have been included in the text written for the president."