Washington ? A joint congressional panel agreed Tuesday to conduct a surprisingly broad probe of intelligence failures surrounding Sept. 11, even as President Bush acknowledged past lapses and sought to curb Congress’s appetite for an ever-widening investigation.

Leaders of the House-Senate panel said they plan to go back 16 years to the days of the Reagan administration in examining what the U.S. intelligence community knew or should have known about terrorist threats to the United States. And the review will also encompass related areas such as last fall’s anthrax attacks along the Eastern seaboard an expansion of the panel’s mandate that stirred sharp debate among lawmakers.

President Bush walks out of the National Security Operations Center with NSA Director Lt. Gen. Michael Hayden during a tour of the National Security Agency in Fort Meade, Md. Bush said Tuesday during the tour of the top-secret agency that the CIA and FBI failed to communicate adequately with each other about possible clues to a terrorist attack before Sept. 11, but said there was no evidence officials could have averted them even with better cooperation.

The aggressive opening of the intelligence panel’s review came as the finger-pointing within the beleaguered intelligence community continued to escalate. A senior FBI official sought to explain to members of Congress at a separate closed hearing why he had failed to connect terror leads in Phoenix and Minneapolis, while CIA officials defended their handling of intelligence information in the weeks and months leading up to Sept. 11.

With Tuesday’s start of closed-door hearings before the joint House-Senate intelligence committee, Congress has now clearly seized control of the debate over whether the U.S. intelligence community missed warning signs that could have allowed authorities to prevent the hijackings.

Congressional investigators have already begun collecting more than 400,000 documents from government agencies, and the agenda laid out by panel leaders Tuesday after their meeting allows them to go back to 1986 the year the CIA’s counterterrorism center was created in examining the U.S. response to terrorism. That period will include the first attack on the World Trade Center in 1993, as well as more recent attacks on U.S. embassies and facilities overseas.

“I think it’s important for us to go back. The farther we go back, the more we learn . . . from our mistakes,” Sen. Richard Shelby of Alabama, ranking Republican on the Senate Intelligence Committee, said in an interview.

The decision to investigate the still-unsolved anthrax attacks as part of the intelligence committee’s scope was something of a surprise and came only after at least one member insisted that it be included, according to a congressional source who asked not to be identified.

“That broadens the scope. The only real debate was over anthrax, and (the members) had to figure out a way to accommodate that,” the source said. The result, part of a seven-point plan developed by the joint panel, was a decision to probe how well the intelligence community has probed biological, chemical, radiological or nuclear threats, including the anthrax attacks.

Shelby said the anthrax attacks which killed five people last fall and have stymied the FBI in its efforts to find a culprit are relevant to the investigation. “I don’t think we should close our eyes to anything. As surely as night follows day, we’ll be hit with biological and chemical weapons,” Shelby said.

Leaders of the 37-member joint panel emerged from their three-hour meeting held in a special sound-proofed room at the Capitol with bipartisan pledges of cooperation, and they condemned the recent rash of finger-pointing within the intelligence community.

Sen. Bob Graham, D-Fla., who heads the Senate Intelligence Committee and will alternate with Rep. Porter Goss, R-Fla., chairman of the House Intelligence Committee, in chairing the hearings called the joint inquiry a milestone for Congress and a rare instance of two standing committees from two chambers working as one. “There is no set of precedents,” Graham said.

“We’re off and running with momentum,” Goss said, promising a “fact-driven, witness-driven” review. Goss said no decision had been made yet on who will testify before the committee, which is scheduled to hold its first public hearings at the end of the month.