In a defeat for President Bush (search), rebellious House Republicans on Saturday derailed legislation to overhaul the nation's intelligence agencies along lines recommended by the Sept. 11 commission (search).

"It's hard to reform. It's hard to make changes," said Speaker Dennis Hastert (search), R-Ill., who sought unsuccessfully to persuade critics among the GOP rank and file to swing behind the measure.

Hastert's decision to send lawmakers home without a vote drew attacks from Democrats and capped an unpredictable day in which prospects for enactment of the measure seemed to grow, then diminish, almost by the hour. He left open the possibility of summoning lawmakers back in session early next month.

The White House urged Congress (search) to keep working on the legislation.

"The president is committed that we do everything possible to build on the intelligence reforms that have already been made," White House deputy press secretary Claire Buchan said.

A compromise approved by key negotiators, the White House and the bipartisan 9/11 commission would have created a powerful position to oversee the CIA and several other nonmilitary spy agencies. A new national counterterrorism center would coordinate the fight against foreign terrorists.

Bush and Vice President Dick Cheney both contacted congressional negotiators by phone in hopes of nailing down a compromise that could clear Congress in the final hours of a postelection session.

But Reps. Duncan Hunter and Jim Sensenbrenner, chairmen of the Armed Services and Judiciary committees, raised objections. Hunter, R-Calif., worried that provisions of the bill could interfere with the military chain of command and endanger troops in the field.

"In my judgment, this bill, without strongly reaffirming the chain of command, would render that area confused to the detriment of our Americans in combat so I will not support it," Hunter said.

Hunter said he knew that the president and Hastert wanted this bill, but "what we have to do here is exercise our best judgment."

Sensenbrenner, R-Wis., wanted additional provisions dealing with illegal immigration. "Unfortunately, the Senate has refused to consider many of the provisions, tagging them as extraneous or controversial," he said.

A group of 9/11 families praised Sensenbrenner for holding out for his illegal immigration provisions.

"Even though the 108th Congress is at its very end, we urge it to let the bill die until the next Congress rather than further weaken the immigration and border security provisions," said the 9/11 Families for a Secure America in a statement.

But another group of 9/11 families called it "unconscionable" that Sensenbrenner and Hunter would stand in the way of the agreement.

"They remain unapologetic as they pursue an agenda that is contrary to the express wishes of President Bush and Vice President Cheney," said a statement from the 9/11 Family Steering Committee.

Sen. Susan Collins of Maine, the primary negotiator on the measure for Senate Republicans, said, "I am very disappointed that these objections have been raised at the 11th hour and temporarily derailed this bill."

Collins said it was surprising, given Bush's recent re-election triumph, that Republicans were not willing to approve legislation that he favored and his aides lobbied for throughout the day.

Democrats were biting.

"The commander in chief in the middle of a war says he needs this bill to protect the American people," said Sen. Joseph Lieberman (search), D-Conn., who led Democratic negotiators.

"Republicans control the House, the Senate, and the White House, and the blame for this failure is theirs alone," said House Democratic leader Nancy Pelosi of California.

If lawmakers fail to pass legislation this year, they will render moot three months of hearings and negotiations that started with the commission's July release of its report studying the Sept. 11 terrorist attacks. Lawmakers would have to start from scratch next year — if they even pick up the issue again. With a new Congress taking office in January, unapproved bills expire and new lawmakers and committee leaders would have to consider any new legislation.