SPANISH PREMIER ORDERS SOLDIERS HOME FROM IRAQ
Spain's new Prime Min Jose Luis Rodriguez Zapatero orders Spanish troops to leave Iraq 'as soon as possible,' keeping a firm campaign promise just 24 hours after he is sworn in; says it is unlikely that United Nations will be playing leading role in Iraq any time soon, which had been his condition for Spain's 1,300 troops to remain; Zapatero's move does not come as surprise to United States, but White House officials say decision is bitter moment for Pres Bush; fear is that Spanish withdrawal will make it more difficult to continue to internationalize forces in Iraq as June 30 date approaches for transfer of soverign power to Iraqi government; Spanish Defense Ministry official says Spanish withdrawal from south-central region around Najaf might take one month; national security adviser Condoleezza Rice voices fear that terrorists could draw 'wrong lesson from Spain' and attempt other attacks aimed at dividing allies; Sen John Kerry, Democrat running for president, expresses regret at Zapatero's decision, noting need for United States to find new coalition partners to share burden in Iraq; photo; chart (M)