The White House may have ignored some aspects of intelligence on Iraq in the run-up to war, former chief US weapons inspector David Kay has suggested.
Last month, Kay said the perception of the Iraqi threat had been "wrong"
He was reacting to a rare speech by CIA director George Tenet, who said the agency had never asserted that Saddam Hussein was an "imminent threat".
A new commission to study intelligence failures should ask whether political leaders manipulated data, Mr Kay said.
President Bush is preparing to announce the membership of that commission.
Administration officials said John McCain - an outspoken senator who ran against Mr Bush for the Republican presidential nomination in 2000 - would be one of its nine members.
The commission will look at the use of intelligence in assessing the threat from Iraq and elsewhere.
However, it is not clear whether its remit will include asking whether the White House made selective use of intelligence or put pressure on analysts.
No 'imminent' threat
In a hastily arranged speech at Georgetown University on Thursday, Mr Tenet defended his agency's intelligence gathering practices and independence, saying it had not been coerced into being alarmist.
No-one told security officials what to say or how to say it, he said, adding: "We always call it as we see it."
Mr Tenet denied his agency had ever said there was an "imminent threat".
Tenet said he was satisfied with the intelligence assessment
Though President Bush himself never used that term, he did variously describe the threat in 2002 as "urgent", "grave" and "unique".
After the war ended, his former spokesman Ari Fleischer insisted the threat had "absolutely" been imminent.
Speaking in Washington on Thursday, Mr Kay said the apparent contradiction "raised the possibility that the intelligence community had been telling the White House one thing and the White House had been hearing something else."
He said the issue of whether politicians manipulated data to make the case for war "is an important question that needs to be understood".
Mr Kay resigned from the leadership of the Iraq Survey Group - sent to track down Iraq's touted weapons of mass destruction - in January.
He subsequently told a US Senate committee that on the question of Iraq's alleged weapons stockpile: "It turns out we were all wrong, and that is most disturbing."
Shortly afterwards, the US National Security Adviser Condoleezza Rice acknowledged there had been flaws in pre-war intelligence.
Days later, President Bush announced his intention to establish an independent commission to look into subject.
Speaking in Charleston, South Carolina, Mr Bush defended the decision to go to war.
"Knowing what I knew then and knowing what I know now, America did the right thing in Iraq," he said.