WASHINGTON — The House broke for a week’s recess Thursday without renewing terrorist surveillance authority demanded by President Bush, leading him to warn of risky intelligence gaps while Democrats accused him of reckless fear mongering.

The refusal of Speaker Nancy Pelosi, Democrat of California, to schedule a vote on a surveillance measure approved Tuesday by the Senate touched off an intense partisan conflict over the national security questions that have colored federal elections since 2002 and are likely to play a significant role again in November.

Trying to put pressure on Democrats, Mr. Bush offered to delay a trip to Africa to resolve the dispute and warned that failure to extend the expanded power under the Foreign Intelligence Surveillance Act, which expires Saturday, could hamper efforts to track terrorists.

“Our intelligence professionals are working day and night to keep us safe,” Mr. Bush said, “and they’re waiting to see whether Congress will give them the tools they need to succeed or tie their hands by failing to act.”

But Ms. Pelosi and other House Democrats said Mr. Bush and Congressional Republicans were at fault because they had resisted temporarily extending the bill to allow disagreements to be worked out. Democrats would not be bullied into approving a measure they considered flawed, she said.

“The president knows full well that he has all the authority he needs to protect the American people,” said Ms. Pelosi, who then referred to President Franklin D. Roosevelt’s admonition about fearing only fear itself. “President Bush tells the American people that he has nothing to offer but fear, and I’m afraid that his fear-mongering of this bill is not constructive.”

The decision by the House Democratic leadership to let the law lapse is the greatest challenge to Mr. Bush on a major national security issue since the Democrats took control of Congress last year.

Last summer, Democrats allowed the surveillance law to be put in place for six months although many of them opposed it. They have also relented in fights over spending on the Iraq war under White House pressure. But with Mr. Bush rated low in public opinion polls as he enters the last months of his presidency, Democrats are showing more willingness to challenge him.

Republicans say House Democrats are taking a risk, especially in light of the strong bipartisan Senate vote for the bill.

“They can’t pass a Mother’s Day resolution and got 68 votes for this bill,” said Representative Adam H. Putnam of Florida, chairman of the House Republican Conference.

The battle over the surveillance bill was also tangled up in the rancor over a House vote to hold in contempt Joshua B. Bolten, the White House chief of staff, and Harriet E. Miers, the former White House counsel, for refusing to testify about the firing of United States attorneys. Republicans said the House was devoting time to that issue when it could be considering the surveillance program, and they staged a walkout in protest.

The main sticking point is a provision in the Senate bill that provides legal immunity for telecommunications companies that, at the Bush administration’s request, cooperated in providing private data after the Sept. 11, 2001, attacks. Many House Democrats oppose that immunity.

Surveillance efforts will not cease when the law lapses. Administration intelligence officials said agencies would be able to continue eavesdropping on targets that have already been approved for a year after the initial authorization. But they said any new targets would have to go through the more burdensome standards in place before last August, which would require that they establish probable cause that an international target is connected to a terrorist group.

Intelligence officials also told reporters Thursday that they were worried that telecommunications companies would be less willing to cooperate in future wiretapping unless they were given immunity.

Ben Powell, general counsel for the director of national intelligence’s office, said some carriers had already asked whether they could be compelled to cooperate even without legal protection, although he indicated that none had actually threatened to halt operations.

Ms. Pelosi said that she believed that the differences could be resolved within three weeks and that she had told the chairmen of the House Intelligence and Judiciary Committees to work with their counterparts in the Senate to seek a compromise.

Congressional Republicans sharply criticized Democrats for not moving on the final measure.

“I think there is probably joy throughout the terrorist cells throughout the world that the United States Congress did not do its duty today,” said Representative Ted Poe, Republican of Texas.

Democrats said Republicans, struggling politically, were trying to create an air of crisis.

“This is a manufactured political crisis,” said Senator Richard J. Durbin of Illinois, the No. 2 Democrat. “They want something to put in front of the American people to take their minds off the state of the economy.”

Eric Lichtblau contributed reporting