LONDON - Acknowledging that neither the United States nor his own government has made a convincing case for deposing Iraq's Saddam Hussein, Prime Minister Tony Blair promised yesterday to provide evidence that the Iraqi leader's interest in weapons of mass destruction poses an imminent threat.
Blair strongly hinted during a news conference that documents could be released "within the next few weeks" that would demonstrate that Iraq has or will soon have the means to produce and deliver biological and chemical agents and that it continues its quest for nuclear weapons.
The prime minister, facing polls that show the public and his own Labor Party overwhelmingly oppose military action, stressed that no decision to attack Iraq has been made. But he insisted that Britain should also take Hussein seriously.
"America should not have to face these problems alone," Blair said. "The whole of civilized society has a responsibility to deal with it."
Blair has long warned about the danger of Hussein's regime, but his blunter remarks yesterday were sure to hearten those in the Bush administration who favor military action.
Support in the United States and Britain for military action has been falling in public opinion polls and among politicians, and support from other European states has been virtually nonexistent.
Blair said he would favor measures other than military action that would diminish the danger posed by Iraq. But he added that weapons inspectors have not been in the country for four years and that Hussein's refusal to agree to allow them back in could be telling.
"There could just be a reason they're not letting the inspections take place," Blair said.
His remarks were made hours after Tariq Aziz, Iraq's deputy prime minister, said his country wanted to negotiate with the United Nations to end the threat of war.
Blair said he would not be satisfied with any arrangements short of "allowing the weapons inspectors back in at any time, any place and anywhere," as Iraq agreed at the end of the Persian Gulf war. "There will be no negotiation of the United Nations resolutions in place," Blair said.
He attributed much of the criticism of President Bush's handling of Iraq policy to "anti-Americanism." He said he decided to make public the evidence against Hussein because the issue is being debated without enough information for reasoned discussion.
"Iraq poses a real and a unique threat to the security of the region and to the rest of the world," he said in a televised 90-minute news conference devoted almost entirely to Iraq. "I would never support anything I thought was wrong out of some blind loyalty to the U.S."
"I do believe that the threat posed by the current Iraqi regime is real," he said. "I believe that it is in the U.K.'s national interest that this is addressed, just as dealing with the terrorists after Sept. 11 was in our national interests even though the actual terrorist act took place thousands of miles away on the streets of New York, not in London."
"I believe there is evidence that they will acquire nuclear weapons if they possibly can," he said.
He appeared to support toppling Hussein if not by military means then by other, unspecified methods.
"Either the regime starts to function in an entirely different way, and there hasn't been much sign of that, or the regime has to change," the prime minister said. "That is the choice, very simply."
Blair's past statements on Iraq have been praised by the opposition Conservative Party but soundly criticized by those in his own ranks.
Michael Ancram, the Conservatives' shadow foreign secretary, told the British Broadcasting Corp. he welcomed Blair's "strong and positive" message and hoped it would resonate with his Cabinet.