WASHINGTON (AP) - In a countdown toward war, President Bush is ready to order a massive military strike against Iraq if Saddam Hussein refuses to surrender power by a deadline of 8 p.m. EST Wednesday. Wary of retaliation, Bush braced Americans for possible terrorist attacks.

On Tuesday, Iraq's leadership rejected Bush's ultimatum. Iraqi television said the decision was made in a joint meeting of the Revolution Command Council and the leadership of the ruling Baath party. Saddam chaired the meeting, it said.

Saddam's elder son, Odai Hussein, said in a statement that Bush is ''unstable'' and ''should give up power in America with his family.''

Bush, in a prime-time speech Wednesday night, vowed to strike Iraq with ''the full force and might'' of the U.S. military unless Saddam and his two sons leave Iraq within 48 hours. More than 250,000 American forces are poised for action in the Persian Gulf. ''The tyrant will soon be gone,'' the president pledged

Senate Democratic leader Tom Daschle charged that a collapse of the administration's diplomatic efforts had brought an unneeded war.

''I'm saddened, saddened that this president failed so miserably at diplomacy that we're now forced to war,'' Daschle said in a speech to the American Federation of State, County and Municipal Employees. ''Saddened that we have to give up one life because this president couldn't create the kind of diplomatic effort that was so critical for our country.''

Bush likened the Iraq threat to those posed by perpetrators of genocide in the last century. ''In this century, when evil men plot chemical, biological and nuclear terror, a policy of appeasement could bring destruction of a kind never before seen on this earth,'' he said.