Defense Secretary Donald H. Rumsfeld warned senators yesterday that moving hastily to centralize all U.S. intelligence-gathering efforts under a new national director could spawn confusion while the country is at war and could prevent vital information from getting to those on the battlefield.

Pledging to work with Congress to "strengthen our ability to live in this new and dangerous world," Rumsfeld said that he believes the Pentagon and the CIA have created a strong, interlocking relationship to close gaps revealed by the Sept. 11, 2001, attacks.

Adding another layer of bureaucracy, he said, could place "new barriers and filters" between the Defense Department's intelligence offices and the field commanders who rely on their data. He added that he prefers having separate agencies that can focus on their specialties rather than a "single and preeminent national intelligence organization."

The testimony before the Senate Armed Services Committee marked Rumsfeld's first appearance in a series of congressional hearings this month on proposals to remake the U.S. intelligence system -- the bulk of which is run by the Department of Defense. The Sept. 11 commission proposed establishing a national intelligence director to oversee the CIA as well as the intelligence offices at the Pentagon and other government agencies.

While Rumsfeld voiced general support for a national intelligence director, he did not stake out a position on what has become a central question in Washington: whether to give such a new chief authority over the budgets and personnel of the 15 intelligence agencies.

The Defense Department accounts for about 80 percent of the $40 billion annual U.S. intelligence budget, including intelligence offices in each branch of the armed services; the Defense Intelligence Agency, which acts partly as clearinghouse for information; the National Security Agency, which intercepts codes; the National Reconnaissance Office, in charge of spy satellites; and the National Geospatial-Intelligence Agency, which exploits and analyzes mapping information.

Rumsfeld said the administration's position on the details of intelligence reform is being worked out.

"It is important that we move with all deliberate speed; however, moving too quickly risks enormous error," Rumsfeld told the committee. "And we are considering these important matters while waging a war. If we move unwisely and get it wrong, the penalty will be great."

Rumsfeld's careful comments reflect a debate that continues within the administration over the details of intelligence reform.

Initially, President Bush embraced the Sept. 11 commission's proposal for an intelligence director and a national counterterrorism center, but officials said he did not want to give the director spending power and hiring-and-firing authority.

Sen. John F. Kerry (Mass.) and other Democrats have called on Bush and Congress to enact the commission's full slate of recommendations, however, and the president's aides have signaled that the White House is considering giving the new director at least some of the authority urged by the commission.

Administration aides acknowledged yesterday the political imperative of responding vigorously to the commission but say they do not want to create problems for future presidents.

"Some want to take a knee-jerk response and say we should just do all this right now," said a senior aide who spoke on the condition of anonymity to be more candid about the decision-making process. "But it's important that you look at all the ramifications of the actions that you're taking. As we move forward quickly, it's important that we do so responsibly, as well."

A Pentagon official, speaking on the condition of anonymity because the Pentagon has not formulated an official stance on the issue, said yesterday that defense officials are embracing the general idea of a new intelligence program.

"It's a great concept, but the ball's in the air right now, and it's too premature to say how it will affect DoD," the official said. "A big part of [the national intelligence director's position] would be DoD. You want to make sure you're putting the right information into the hands of the people on the ground who pull the trigger so they are the best they can be."

At yesterday's hearing, acting CIA Director John E. McLaughlin also urged a deliberate approach. He said his agency and the Pentagon have worked over the past three years to break down barriers and coordinate efforts at home and overseas -- improvements he said addressed many of the shortcomings identified by the Sept. 11 commission.

"Speed and agility are not promoted by complicated wiring diagrams, more levels of bureaucracy, increased dual hatting or inherent questions about who is in charge," McLaughlin said. "I believe that short, clear lines of command and control are required in whatever structure you establish, regardless of what you call its leader." McLaughlin took over at the CIA after the retirement of George J. Tenet. Bush has nominated Rep. Porter J. Goss (R-Fla.) to become the next director of the CIA, a job that would change considerably if a national intelligence director were in charge of all U.S. intelligence agencies.

Several members of the Senate Armed Services Committee agreed yesterday that changes should be the result of careful study.

Committee Chairman John W. Warner (R-Va.) said that he wants action soon to strengthen intelligence to confront a constant and evolving threat of terrorist attack. But he said he did not want to offer drastic changes that could cause "turbulence or disruption in the intelligence system" when the nation is at war.

Among the options, Warner said, are creating a national director as proposed by the commission, or a less dramatic reorganization that would give the CIA director greater authority over budgets and the activities of other intelligence agencies, an approach similar to that in legislation proposed by Goss and others.

Sen. Carl M. Levin (D-Mich.) said he hopes Congress will focus on the structure of the intelligence community and on how intelligence has been used by the administration.

"As we consider legislation for the reorganization of the intelligence community, we should recognize the significance of both types of failures: those resulting from poor organization and management, and those resulting from politicizing intelligence," Levin said.

Air Force Gen. Richard B. Myers, chairman of the Joint Chiefs of Staff, told the committee that reorganizing the intelligence community is an obviously complex and difficult task. He implored Congress to remember that the military depends on intelligence on a scale unparalleled in the government.

"As we get more and more clarity on the gaps and deficiencies in our intelligence today, we have to guard against creating new problems," Myers said. "And the details matter very much."

Sen. John W. Warner (R-Va.), left, and Defense Secretary Donald H. Rumsfeld speak before a hearing of the Senate Armed Services Committee, of which Sen. Elizabeth Dole (R-N.C.) is a member. Warner suggested a less dramatic reorganization than a centralization of U.S. intelligence gathering.