"Iraq poses a real and a unique threat to the security of the region and to the rest of the world," Blair told a news conference. "This is not just an issue for the U.S. It is an issue for Britain and the wider world."
Blair said Saddam was violating United Nations resolutions and was continuing "in his efforts to create weapons of mass destruction."
"We cannot have a situation where people turn a blind eye," he added.
Meanwhile, Iraq today made it clear it wants to avert war with the United States, CBS News Correspondent Elizabeth Palmer reports.
Tariq Aziz, Iraqi deputy prime minister, says, "We are taking the threats very seriously."
So seriously in fact that the Iraqi leader hijacked center stage at the World Summit in Johannesburg to hint at a compromise with the U.S. through weapons inspections
Aziz says, "We are ready to cooperate with the United Nations"
It's not clear whether this is a genuine concession or simply a delaying tactic. Observers note Aziz is a veteran of this kind of brinkmanship. He may have chosen the conference here in Johannesburg to make his latest offer because of the world leaders gathered here. Many of them -- if not out and out supporters of Iraq -- are at least critics of America's recent sabre rattling.
Nelson Mandela says, "I have not given up that I will be able to persuade President George Bush. No country should be allowed to take the law into their own hands"
An opinion echoed by many US allies in Europe -- France, Germany among those that head the list along with Russia, Japan and China. In the Middle East countries such as Saudi Arabia, Bahrain, Egypt and Yemen are opposed and closer to home, so is Canada.
Essentially, Blair stands alone in his show of support for President Bush.
Commentators suggested Blair's remarks are an attempt to rally international support for action against Iraq, as other countries raise doubts in Europe and elsewhere about the wisdom of going to war.
Russia said Monday it would veto any measure for military action against Baghdad that comes up before the U.N. Security Council.
"We hope ... that this question will not be placed to the Security Council, thereby necessitating the veto of Russia," Russian Foreign Minister Igor Ivanov said after meeting his Iraqi counterpart, Naji Sabri, in Moscow.
But Ivanov also pressed Baghdad to allow the return of U.N. weapons inspectors, which he said was a "necessary condition" for lifting sanctions.
French President Jacques Chirac has said that any military action against Iraq be decided by the U.N. Security Council. German Chancellor Gerhard Schroeder, an outspoken critic of an invasion, has called on the White House to consult fully with allies on its plans.
Kofi Annan on Tuesday met with Aziz, urging him to comply with Security Council resolutions, which call for the unconditional return of inspectors, Annan's spokeswoman said.
Resuming inspections "in turn will lead to a comprehensive solution, including the lifting of sanctions," Annan's office said.
Aziz accused Washington of being uninterested in dialogue over the weapons issue, which he said the United States was using as an excuse for military action.
"In the end, they will use whatever pretext remains in their hands to attack us," he said. "We are preparing ourselves to defend our country.
"We invited the Americans themselves, we invited the British to come. If they come for a special mission they are welcome because that is what we want them to do. But if they send people who will drag their feet for years without reaching a conclusion as they did for seven-and-a-half, that's not going to work."
Britain is one of the United States' strongest allies, but Blair has barely spoken in public about Iraq in recent weeks. He has come under mounting pressure from the British news media and members of his own governing Labor Party to explain his position.
Facing a barrage of questions from journalists about Britain's position on Iraq, Blair said inaction was not an option but insisted no decision had been made what to do.
"I do believe that the threat posed by the current Iraqi regime is real, 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 interest even though the actual terrorist act took place thousands of miles away on the streets of New York, not in London," he said.
"The whole of the international community has a responsibility to deal with this," Blair said.
"If Sept. 11 teaches us anything, it teaches us that it is wrong to wait until the threat materializes," he said. "These issues are being raised rightly by the United States."