WASHINGTON – Leaders of the Sept. 11 commission urged senators Friday to embrace their politically sensitive proposals for massive changes to the nation’s intelligence structure, warning that bureaucratic wrangling leaves America dangerously vulnerable to another terrorist attack.

The unusual hearing – coming during summer recess on Capitol Hill – focused on two of the commission’s most complex proposals: the creation of a new national counterterrorism center and a new national intelligence director to oversee the 15-agency intelligence community.

“We have concluded the intelligence community is not going to get its job done unless somebody really is in charge,” said Lee Hamilton, the Democratic vice chairman on the commission. “That is just not the case now, and we have paid the price.”

Thomas Kean, the commission’s Republican chairman, described a litany of failures by the intelligence community in the months preceding the 2001 terror attacks against New York and Washington. He attributed failures to a profound lack of coordination across intelligence agencies.

“No one was the quarterback, no one was calling the plays,” Kean said. He said that in the proposed reorganization, “each agency needs to give up some of their existing turf and some of their authority.”

Kean said an assertion by recently departed CIA Director George Tenet that it will take five years to reform intelligence was “unacceptable.”

However, Kean and Hamilton praised reforms already undertaken by FBI Director Robert Mueller, who has sought to transform the bureau’s priority from criminal investigations to counterterrorism.

But Kean worried what might happen if Mueller and his top deputies leave, saying he was fearful the bureau would revert to its historical emphasis on chasing white-collar criminals, mobsters and bank robbers.

“A lot of the FBI would like to go back, if you would, to breaking down doors again,” Kean said.

Senators pledged to quickly but thoughtfully consider the commission’s proposals.

“We must react with speed but not in haste,” said Sen. Susan Collins, R-Maine, the chairwoman of the Governmental Affairs Committee. She also urged lawmakers to “be bold but not reckless” in considering changes that will lead to what she described as a “fundamental overhaul of our intelligence structure and a sea change in our thinking.”

The committee’s ranking Democrat, Joseph Lieberman of Connecticut, promised that “We’re going to get this job done and get it done with unprecedented thoughtfulness and speed.”

Collins said she supports the idea of an intelligence director, though has questions about how the office would be set up.

“Massive reorganizations are always controversial,” Collins said. “While turf battles abound in Washington, for the American people it is results that count. Power struggles for authority and responsibility – however well motivated – cannot be allowed to doom needed reforms.”

The proposal for a new intelligence director and establishing a counterterrorism center that could be run out of the White House likely would take power away from two dominant forces in the intelligence community, the CIA and the Defense Department.

Under public and political pressure to enact changes, President Bush created a working group to study the commission’s recommendations and draft executive orders that could immediately implement some of the proposals.

That group was meeting again Friday and nearing completion of its work, White House spokesman Scott McClellan said.

In Miami, Homeland Security Secretary Tom Ridge said Friday the administration was open to additional changes.

“I think right now, for our purposes, everything is out on the table,” Ridge said. “If there’s still gaps there, if we need to do it, then we need to work with Congress and use the recommendations as a starting point for that conversation.”

Other commission proposals include disclosing now-classified intelligence budget figures and institutionalizing changes ongoing at the FBI.

The Sept. 11 attacks already have prompted the largest government reorganization in 50 years with the opening of the Homeland Security Department, which celebrated its one-year anniversary in March.

The hearing is the first of at least 15 that will be held in the coming weeks by more than a half-dozen House and Senate committees. Collins said the Republican Senate leadership has encouraged her to stay focused on the national intelligence director and counterterrorism center proposals and try to produce a bill by Oct. 1.

Congressional aides also are examining a series of issues related to the proposals. Among them:

. What role will the national intelligence director have in setting policy, not traditionally the territory of intelligence officials?

. Will that person brief the president?

. Should the individual be on the Cabinet? How will its deputies and other related offices be structured?