Colin Powell at the Nato headquarters in Brussels. . (AFP)

Washington, April 3 (Reuters): US secretary of state Colin Powell acknowledged today that the “most dramatic” part of his presentation to the UN making the case for war on Iraq was based on flawed intelligence.

Powell also said he hoped a commission investigating the US intelligence on Iraq’s alleged weapons of mass destruction would reveal how the CIA ended up depending on unreliable sources for key evidence he used to argue for war.

The acknowledgment about alleged mobile chemical arms laboratories could further hurt the credibility of the Bush administration, also under fire in an election year for failing to stop the September 11 attacks.

The United States justified its first pre-emptive war by accusing Iraq of amassing illegal arms and invaded last year without explicit UN approval and over the objections of many allies.

In February, 2003, Powell made a major presentation of the US case against Iraq at a special session of the UN Security Council, where he said the US had several sources showing mobile chemical weapons laboratories.

But yesterday, the top American diplomat said the evidence on the trailers has been shown to be shaky. “Now it appears not to be the case that it was that solid. But at the time I was preparing that presentation it was presented to me as solid,” Powell said on a flight home from a trip to Europe.

While doubts about the US sources of evidence for the laboratories have been raised for over a year, Powell’s remarks were the most straightforward acknowledgment from the Bush administration that the information was probably wrong.

“That was the most dramatic of them (pieces of evidence) and I made sure it was multi-sourced,” he said. “Now if the sources fell apart, then we need to find out how we’ve got ourselves in that position.”

“I hope (the commission) will look into these matters to see whether or not the intelligence agency had a basis for the confidence that they placed in the intelligence at that time,” he said.

The failure to unearth banned weapons a year after the invasion has fuelled criticism of the Bush administration for misleading the country into a war that caused hundreds of US deaths and sparked a deadly insurgency against the American occupation.

Despite being one of the administration’s most respected officials, Powell’s credibility has suffered because many critics saw him as the mouthpiece for the intelligence community over Iraq. Powell sought yesterday to distance himself from the evidence he used in his UN presentation. “I’m not the intelligence community,” he said.

Police chief killed

Gunmen killed a police chief in Baghdad today, the second to be shot dead in 24 hours and the latest in a growing list of security officers killed by insurgents who target anyone linked to Iraq’s occupiers.

Police said the police chief of Mahmudiya, south of Baghdad, was shot after leaving his home in the capital. His car was riddled with bullets. Last night, the police chief in Kufa, further south, was shot dead along with a colleague.

Insurgents fighting the occupation have increasingly targeted members of the US-trained fledgling Iraqi security forces. More Iraqi security officials have been killed in the past year than American soldiers.

The US-led authorities in Iraq have warned attacks are likely to increase ahead of the planned transfer of sovereignty to Iraqis on June 30. The US military says it has stepped up operations in reaction to the latest uptick in violence.