In Washington, two Senate committees will soon hold joint hearings on the prewar intelligence. Opposition politicians in Australia want a similar inquiry.
British Prime Minister Tony Blair faces accusations from anti-war lawmakers in his own party that he hyped the threat from Iraq's weapons to justify war.
Iraq's alleged illegal arsenal was a leading reason quoted by the three governments for invading the country, along with Saddam Hussein's alleged links to terrorists and human rights record.
In a final report to the United Nations this week, chief inspector Hans Blix says his teams found no evidence of illegal weapons, but did have additional questions when they were forced to abandon their work because of the war.
While two possible mobile biological weapons production factories have been found, no other evidence has been located in visits to 300 sites by U.S. teams.
Last week, Defense Secretary Donald Rumsfeld said Saddam may have destroyed his weapons before the war. His deputy, Paul Wolfowitz, told Vanity Fair magazine that the WMD argument was adopted for "bureaucratic reasons," but later claimed to have been misquoted.
President Bush said this weekend that weapons had been found. As evidence, however, he pointed to the two suspected mobile biological laboratories, which both the Pentagon and American weapons hunters have said do not constitute arms.
Secretary of State Colin Powell this week referred to Iraq's past possession of weapons.
There are smoking guns all over. Remember, Iraq has weapons of mass destruction. We found them in 1991," he told a Rome television station Monday. "They have weapons of mass destruction, they've had them, they used them against Iran. That is not disputable."
The Senate Armed Services Committee will hold join hearings on the matter with the Intelligence Committee, perhaps as soon as this month, Agence France Presse reports.
In Australia, Defense Minister Robert Hill told the Sydney Morning Herald. "If it turns out there were flaws in what we understood, then I think we ought to say there were flaws. But it's too early to say that."
The paper said all opposition parties in Australia are backing an investigation.
In Britain, controversy has focused on a government dossier, published in September, outlining evidence that Iraq had weapons of mass destruction and plans to deploy them on 45 minutes' notice.
More than 50 Labor lawmakers have signed a Commons motion drafted by Peter Kilfolye, a former Labor defense minister, calling on the government to publish the evidence behind the dossier.
The Liberal Democrats, the third-largest party in Parliament, have called for a public inquiry. The main opposition Conservative Party has not endorsed an inquiry, but has urged Blair to publish any additional evidence to support the claims made before the war.
Tony Wright, a member of Blair's Labor Party and chairman of the Commons Public Administration Committee, said an inquiry was now "almost inevitable."
A spokesman for Blair said the prime minister "did not see the need for an independent inquiry of the nature being demanded." Blair has emphatically denied doctoring the evidence.
In the report to the Security Council Monday, Blix said U.N. inspectors "did not find evidence of the continuation or resumption of programs of weapons of mass destruction or significant quantities of proscribed items."
But, he said, the inspectors had many questions about its chemical and biological programs when they left shortly before the March 20 invasion.
Inspectors also didn't have time to follow up on some late information provided by the Saddam government — including interviewing a list of Iraqis who helped destroy anthrax after the 1991 Gulf War, he said.
U.N. inspections uncovered "a small number of undeclared empty chemical warheads which appear to have been produced prior to 1990," Blix said.
These were destroyed along with a few other proscribed items and some 70 Al Samoud-2 missiles with a range beyond the 92-mile limit allowed under U.N. resolutions.
While Iraq's cooperation with U.N. inspectors started improving in late January and inspectors got "a better understanding of past weapons programs," Blix said, "little progress was made in the solution" of outstanding disarmament issues.
Extensive excavations by the Iraqis, which were witnessed by U.N. inspectors, showed that Iraq had destroyed a large number of R400 bombs containing a biological agent, as it had claimed. But the excavations couldn't verify the amount of agent produced or destroyed, he said.
Similarly, an Iraqi chemical analysis of soil samples from the site where anthrax was declared to have been dumped in 1991 showed it had been dumped there.
Blix said U.N. inspectors also didn't have time to complete their investigation on whether pilotless Iraqi drones were designed to disperse chemical or biological weapons, or had a range beyond the 92-mile limit.