The White House and senators from both parties raised objections on Friday to one of the key reforms recommended by the Sept. 11 commission, even as the panel's leaders warned that the nation would remain at greater risk of terrorist attack unless the changes are enacted quickly.

The criticisms from Capitol Hill and the Bush administration represent the first significant challenge to a central recommendation of the Sept. 11 commission, which argues in its 567-page final report that a single intelligence director should work out of the president's office to coordinate the war on terrorism.

During the first congressional hearing on the issue on Friday, several GOP and Democratic lawmakers raised concerns about that idea, saying that placing an intelligence director and a national counterterrorism center inside the Executive Office of the President could increase the potential for misuse of information and could threaten the independence of U.S. intelligence analysts.

At the White House, where officials are formulating their own package of reform proposals, a senior official, speaking on background to reporters, indicated that the administration will oppose any such arrangement. The official said Bush "wants to protect intelligence agencies from any undue influence" and "ensure that intelligence analysts maintain their autonomy."

"It is fair to say that there [are] some very important potential consequences to the placement of the office," the White House official said.

But the commission's leaders, Chairman Thomas H. Kean (R) and Vice Chairman Lee H. Hamilton (D), staunchly defended the proposal during their first congressional testimony on the panel's recommendations, telling the Senate Governmental Affairs Committee that congressional oversight and other safeguards would help ensure that intelligence information is not politicized by the White House.

Kean and Hamilton urged the senators to act quickly to adopt the Sept. 11 commission's reforms, arguing that the nation is at greater risk of a terrorist attack the longer the lawmakers wait.

"These people are planning to attack us again, and trying to attack us sooner rather than later," Kean said. "Every delay we have in changing structures or changing people, or whatever it is, to make that less likely is a delay the American people can't tolerate."

The emerging criticism of the commission's intelligence-director proposal does not necessarily pose a threat to the panel's other recommendations, which range from a general reorganization of the intelligence community to expensive improvements in the nation's border control system. But Hamilton and other commission officials have stressed that the recommendations should be considered as a whole package and should not be significantly altered.

"We have concluded that the intelligence community is not going to get its job done unless somebody is really in charge," Hamilton said. "That is just not the case now, and we paid the price."

Bush and senior aides have been meeting regularly over the past week to hammer out changes that can be ordered by the president on his own as early as next week. Democratic presidential contender John F. Kerry, meanwhile, has endorsed the panel's entire reform package and has criticized Bush for not moving more quickly to implement the changes.

At the governmental affairs panel, ranking members Susan Collins (R-Maine) and Joseph I. Lieberman (D-Conn.) vowed on Friday to rapidly prepare legislation that would incorporate many of the Sept. 11 panel's suggested reforms.

While many of the panel's proposals have proved popular, its call to place the war on terrorism more firmly under presidential control has produced an odd alliance of detractors inside and outside the intelligence community. In addition to spurring opposition from the Bush White House -- which has zealously guarded executive power during its tenure -- the idea has prompted criticism from some Democrats and from the American Civil Liberties Union.

"If we act hastily to appease partisan pressures, we could create a surveillance society with an intelligence czar in the hip pocket of the president," Anthony D. Romero, the ACLU's executive director, said in a statement on Friday.

Some of the sharpest questioning about the intelligence-director proposal came from Sen. Carl M. Levin (D-Mich.), who sits on the governmental affairs, intelligence and armed services committees, all of which will play major roles in crafting reform legislation in the Senate. Levin told Kean and Hamilton that "a top priority of reform must be greater independence and objectivity of intelligence analysis" that is "not tainted by the policies of whatever administration is in power."

Hamilton said later that "there's no magic solution here, and every move you make has some advantages and has some disadvantages. We think the advantages, number one, of sharing information, and number two, of having someone in charge of managing the situation, is critical, and you don't have that today."

Collins, the committee's chairman, told reporters after the hearing that she had not made up her mind about where a new intelligence director should be located within the government.

"I thought that the chairs made a very strong case for placing the position within the Executive Office of the President and for having the individual serve at the pleasure of the president," she said. "But I'd want to hear more testimony on those two points."

The White House official said Bush has already taken some of the steps recommended by the commission and will soon announce additional steps stemming from the administration review. "They may well go beyond what the commission recommended" in the area of intelligence reorganization, the official said.