An agreement announced by leading lawmakers to form an independent commission to investigate the Sept. 11 attacks fell apart late Thursday after the chairman of the House Intelligence Committee said more details needed to be worked out.

The agreement would have given the commission a broader scope and more time than the often-frustrating inquiry lawmakers are now winding down.

On Thursday, the House and Senate Intelligence Committees conducting the inquiry met with the CIA and FBI directors, discussing the handling of an informant who was the landlord of two Sept. 11 hijackers. Lawmakers have been bothered both by the handling of the case and their difficulties in obtaining information about it.

The independent commission was announced at a news conference by three of the four leaders of the intelligence committees, who assured that the fourth, Rep. Porter Goss, the chairman of the House committee, had also agreed to the plan. Leaders of the Senate Governmental Affairs Committee, Sens. Joseph Lieberman, D-Conn., and John McCain, R-Ariz., also said an agreement had been reached.

But after the White House and House Republican leaders raised concerns about the commission, Goss told members of the two committees that more issues needed to be resolved.

Goss, R-Fla., later told reporters the only agreement reached Thursday was on four particular issues involving the commission. "We haven't gotten quite full agreement yet," he said.

The leading House advocate for the commission, Rep. Tim Roemer, D-Ind., blamed the Bush administration for blocking the agreement.

"I worry that the White House is trying to pull the carpet over the independent commission and do the slow roll and kill it," he said.

Governmental Affairs committee spokeswoman Leslie Phillips said Lieberman "was surprised and disappointed to learn that the deal had collapsed because he had been informed earlier in the day that there was a bipartisan agreement."

Both the House and Senate have voted for an independent commission, though the two versions differ. The administration initially opposed a commission, but announced last month it would support it. Lawmakers have been meeting with White House officials to work out the commission's structure and scope.

Lawmakers said Thursday morning that talks with the White House broke down. But by afternoon, they said intelligence committee leaders had worked out an agreement among themselves, which they would try to add to a bill authorizing 2003 intelligence programs.

But the White House said no agreement had been reached with them and John Feehery, a spokesman for House Speaker Dennis Hastert, said Republican leaders were still trying to work out consensus in Congress.

Under the plan announced Thursday, the commission would have consisted of 10 members with two co-chairmen, one appointed by the president, the other by the Democratic leader of the Senate, and have a two-year mandate. The commission would look into issues such as intelligence, commercial aviation, and immigration.

The joint inquiry of the intelligence committees began in February and has a one-year mandate. Its scope is limited to intelligence issues related to the attacks.

Many lawmakers have complained that the committee's work has been hampered by difficulty in receiving information from intelligence agencies.

Sen. Evan Bayh, D-Ind., declined to discuss details of Thursday's meeting with FBI Director Robert Mueller and CIA Director George Tenet, but said he believed it helped ease members' doubts.

"There have been some communications problems, but I don't detect a systematic effort to deceive," he said.

The chairman of the Senate Intelligence Committee, Sen. Bob Graham, D-Fla., said concerns about communications problems were aired at the hearing. Asked if he was satisfied with the cooperation, he said, "I think it is allowing us to get our job done."

The Senate committee's top Republican, Sen. Richard Shelby of Alabama, said cooperation from intelligence agencies "has been spotty at best. We have to extract bit by bit, piece by piece any information, it seems."