Blair, who has been attempting to persuade a reluctant Britain - and Europe - to support President Bush's stand against Hussein, presented Parliament with a 50-page dossier on Iraq compiled by British intelligence agencies.
"And if people say: why should Britain care?" Blair said, "I answer: because there is no way that this man, in this region above all regions, could begin a conflict using such weapons and the consequences not engulf the whole world."
Blair had summoned the House of Commons from recess into a one-day emergency session to discuss Iraq after a significant number of his party members went public with doubts about military action.
"His weapons of mass destruction program is active, detailed and growing," Blair told Parliament, and he said the only way to get Hussein to agree to inspections was with credible threats of force.
"Our case is simply this: not that we take military action, come what may, but that the case for ensuring Iraqi disarmament - as the U.N. has stipulated - is overwhelming," Blair said. "I defy anyone on the basis of this evidence to say that is an unreasonable demand for the international community to make when, after all, it is only the same demand that we have made for 11 years and he has rejected."
The United States and Britain are preparing a United Nations resolution that would call for military action if Hussein does not disarm. Blair said it could be ready as early as this week.
The Iraqi culture minister, Hammed Youssef, said in Baghdad that the allegations in the dossier were untrue, the Associated Press reported.
"The British prime minister is serving the campaign of lies led by Zionists against Iraq," Youssef said. "Blair is part of this misleading campaign."
Blair said the chemical and biological weapons are an immediate threat, and he warned that Hussein, in defiance of U.N. resolutions, was attempting to develop ballistic missiles that could travel as far as Turkey, Greece and Cyprus, where British military forces are gathered.
U.N. inspectors said before leaving Iraq in 1998 that Hussein likely had chemical weapons and the means to transport them without difficulty. A spokesman in the prime minister's office said the 45-minute window is a new assessment that shows "a degree of sophistication" not previously reported.
Blair's report also detailed previous claims that Iraq was shopping the globe for ingredients needed for a nuclear weapon. He said Iraq had approached unnamed countries in Africa for uranium and was looking elsewhere for vacuum pumps needed to enrich it. Whether he obtained uranium is unknown.
With help, the report said, Hussein could have nuclear weapons within months.
Although backed by the Conservative Party, Blair has faced considerable opposition from other members of Parliament, including a sizeable number from his own ruling Labor Party, who fear Britain is rushing headlong into war with Iraq.
During debate yesterday, Liberal Democrat leader Charles Kennedy warned against any action against Iraq without full backing from the United Nations. He accused Blair of slavishly following the whims of Bush and warned against going against Iraq alone.
"Those of us who have never subscribed to British unilateralism are not about to sign up to American unilateralism now, either," Kennedy said, adding that Bush's aim of "regime change" would "create a dangerous precedent in international affairs."