CRAWFORD, Tex. — For months President Bush harangued Democrats in Congress for not moving quickly enough to support the troops and for bogging down military bills with unrelated issues.

And then on Friday, with no warning, a vacationing Mr. Bush announced that he was vetoing a sweeping military policy bill because of an obscure provision that could expose Iraq’s new government to billions of dollars in legal claims dating to Saddam Hussein’s rule.

The decision left the Bush administration scrambling to promise that it would work with Congress to quickly restore dozens of new military and veterans programs once Congress returns to work in January.

Those included an added pay raise for service members, which would have taken effect on Tuesday, and improvements in veterans’ health benefits, which few elected officials on either side want to be seen opposing.

Mr. Bush’s veto surprised and infuriated Democratic lawmakers and even some Republicans, who complained that the White House had failed to raise its concerns earlier.

And it gave Democrats a chance to wield Mr. Bush’s support-the-troops oratory against him, which they did with relish.

“Only George Bush could be for supporting the troops before he was against it,” Senator John Kerry, Democrat of Massachusetts, said in a statement, reworking a familiar Republican attack during his unsuccessful presidential campaign in 2004 that he supported the war in Iraq before he turned against it.

The veto was an embarrassment for administration officials, who struggled on Friday to explain why they had not acted earlier to object to the provision, Section 1083 of a 1,300-page, $696 billion military authorization bill. It would expand the ability of Americans to seek financial compensation from countries that supported or sponsored terrorist acts, including Libya, Iran and Iraq under Saddam Hussein.

It was unclear how the provision had been overlooked by White House lawyers. A senior administration official told reporters in a hastily arranged conference call that the bill’s consequences for Iraq came into “acute focus” only a week to 10 days ago — after Iraqi officials complained to the American ambassador in Baghdad, Ryan C. Crocker. The White House said President Bush had recently spoken with Prime Minister Nuri Kamal al-Maliki of Iraq about the consequences of the provision.

It was also an embarrassment for some in Congress, including Republican senators who sponsored the provision, like John Cornyn of Texas and Ted Stevens of Alaska. Republicans joined Democrats in overwhelmingly approving the broader military bill, but they backed the White House on Friday. Senator John W. Warner of Virginia, who led Republicans in drafting the military policy bill, said that he was now swayed by the administration’s arguments that it could endanger Iraq’s new government.

“The White House prepared a very detailed legal memorandum, and I am convinced that they are correct,” Mr. Warner said in a telephone interview.

While removing the provision would involve only a minor amendment, the veto could reopen many of the contentious issues that stalled the legislation’s approval in the first place, including efforts by Democrats to impose conditions on spending for the military operations in Iraq.

At a minimum, the veto will provoke a fight over an issue that was put into the legislation after no public debate. The Senate sponsor, Frank R. Lautenberg, Democrat of New Jersey, expressed strong support for the provision on Friday, saying it would help plaintiffs in lawsuits against Iran and Libya, including relatives of Americans killed in the bombing of the Marine barracks in Beirut in 1983 and in the bombing of a Berlin disco in 1986.

“My language allows American victims of terror to hold perpetrators accountable — plain and simple,” said Mr. Lautenberg, who has long championed expanding legislation to let victims sue foreign governments.

In a “statement of disapproval,” or pocket veto that lets the bill expire on Dec. 31, Mr. Bush said that the provision could result in preliminary injunctions freezing Iraqi assets in American banks — $20 billion to $30 billion, according to a senior administration official — and even affect commercial ventures with American businesses.

He also warned that it was written to revive dormant legal claims, including a $959 million judgment won by American pilots who were prisoners of war during the Persian Gulf war in 1991. The administration had declared the new government exempt from claims dating to Mr. Hussein’s government, which the United States overthrew in 2003.

“Exposing Iraq to such significant financial burdens would weaken the close partnership between the United States and Iraq during this critical period in Iraq’s history,” Mr. Bush said in his statement.

A senior administration official said, “The Iraqis certainly did raise very serious and strong concerns about this, which were confirmed as we really dived into this and gamed out the consequences.” The White House allowed the official to speak only if not identified.

Mr. Bush’s aides have already begun negotiations with Congress to remove the provision or rewrite it to exempt Iraq and enact the bill’s other provisions. The White House chief of staff, Joshua B. Bolten, and national security adviser, Stephen J. Hadley, spoke with Republican lawmakers in a conference call on Friday to explain the president’s decision and to build support for quick Congressional action next month, Mr. Warner said.

The White House also said it would make an added raise Congress approved for service members — a half-percent above the 3 percent increase that will take effect regardless — retroactive to Jan. 1, 2008, no matter when a final bill is approved.

The final military spending bill was adopted by overwhelming margins, 370 to 49 in the House and 90 to 3 in the Senate.

It was Mr. Bush’s eighth veto, an executive power he has used with greater frequency with Democrats in control of Congress. Because he used a pocket veto — allowing the legislation to expire 10 days after it was passed by the House — his decision cannot be overridden. Adding to the uncertainty, Brendan Daly, a spokesman for the House speaker, Nancy Pelosi, said Friday evening that the House was reserving its right to schedule an override vote anyway, arguing that the president’s pocket veto was not legally viable.

Mr. Daly said House officials believed that, under their interpretation of the rules, Mr. Bush technically could not use his power to pocket veto the measure.

Still, Ms. Pelosi and the majority leader, Senator Harry Reid of Nevada, indicated that Democrats hoped to move swiftly to address the concerns of the White House and get the bill back to the president for his signature. The House returns on Jan. 15 and could send a revised version of the bill to the Senate by the time it returns a week later.

Some lawmakers accused the administration of siding with the Iraqi government over Americans who had suffered in terrorist attacks, a sensitive charge for a president who has made the fight against terrorism the central theme of his presidency.

“It is a shame,” Representative Ike Skelton, Democrat of Missouri, the chairman of the Armed Services Committee, said in a statement, “that the White House has taken this step to satisfy the demands of the Iraqi government for whom our troops have sacrificed so much.”

Steven Lee Myers reported from Crawford, and David M. Herszenhorn from Washington.

Copyright 2007 The New York Times Company