The US Justice Department said it had opened a criminal investigation on Tuesday into the leak of a CIA agent's identity allegedly to try to deflect criticism of the war, a case very similar to one that has shaken British Prime Minister Blair.
Bush said after meeting business leaders in Chicago he wanted anyone with information about what Justice Department lawyers termed "possible unauthorised disclosures concerning the identity of an undercover CIA employee" to come forward.
"If anybody's got any information inside our administration or outside our administration, it would be helpful if they came forward," Bush said in his first public comment on the issue.
The controversy centres on the disclosure that Valerie Plame - the wife of Joseph Wilson, a former US ambassador to Gabon - was an undercover CIA operative, specialising in weapons of mass destruction.
Wilson, a critic of prewar intelligence on Iraq, says his wife's cover was blown by administration officials looking to discredit him.
Seeking to appease
In Britain, Blair defended his position on the Iraq war, which he acknowledged had divided the nation and the world.
The speech aimed to repair damage done by the British leak of the identity of a government expert in Iraqi weapons of mass destruction who had anonymously questioned the handling of pre-war intelligence to a journalist.
A judicial inquiry was launched after the expert committed suicide.
Party leaders have headed off a full-scale debate on Iraq at the Labour conference, but anti-war campaigners plan to get in their challenge when Foreign Secretary Jack Straw and Defence Secretary Geoff Hoon address the gathering on Wednesday.
Tony Blair confident he can regain
Both investigations are a blow to Bush and Blair as they seek to destroy armed resistance in Iraq and share out the costs of rebuilding the country by drafting a new resolution for the United Nations Security Council to consider.
France and Germany have led calls for Washington to transfer power from US-led occupation forces to an Iraqi government within months as a condition for supporting a resolution in the Security Council.
Washington, which says the new draft could be ready within days, is trying to address their concerns with a roadmap for handing power to Iraqis.
But Iraqi officials said on Tuesday a key prerequisite of self-rule, a constitution, would take much longer to draft than the six-month target Washington has suggested in an attempt to win wider international backing.
Iraq's US-led administration said no deadline was being set on a constitution and a spokesman for outgoing Iraqi Governing Council chairman and convicted fraudster Ahmad Chalabi told a news conference six months was not enough to write it.
A committee charged with deciding how a constitution should be drawn up will hand its report to the Governing Council on Wednesday, a day later than planned, officials said. The council will then choose between the options.
Divisions have opened up between the United States and some Governing Council members over how and when power should be handed back to Iraqis.
Some say the Council should be formally recognised as a sovereign Iraqi government, even before a constitution is written and elections held.