Centrifuges

The Bush administration in 2002 said that Saddam Hussein was buiding a nuclear program. The only physical evidence was high-strength aluminum tubes that they claimed were to be used in centrifuges in the
uranium enrichment process.
The government's foremost nuclear experts contradicted the supposition that the tubes were intended for purifying materials for nuclear weapons, but that they were probably to be used for artillery rockets.
When Bush took office as President, the intelligence agencies agreed that Iraq was no longer pursuing a nuclear weapons program. Sanctions and inspections since the Gulf War had seen to the cessation of Iraq's nuclear ambitions.
A worker in the CIA. reported that centrifuges sought by Saddam Hussein had no use other than in a uranium enrichment program. That statement was challenged by the nuclear experts in the US Energy Department, specifically that they did not match the specifications for use in a centrifuge, but did match tubes that Iraq had used previously for making rockets.
Experts were sent to examine some tubes that were apprehended and wrote a report that expressed detailed doubts about their suitability for a nuclear program. Similar conclusions were reached by British intelligence and the United Nations International Atomic Energy Agency. The latter pointed out the CIA worker's errors in analysis and sent a copy of their report to the US government.
Excerpted and adapted from:
How the White House Embraced Disputed Arms Intelligence