WASHINGTON (AP) – President Bush on Friday appointed former Secretary of State Henry Kissinger to lead an investigation into why the government failed to foil the Sept. 11 attacks, telling the veteran diplomat to “follow all the facts wherever they lead.”

Signing a bill he once opposed, Bush told survivors and victims’ family members, “We must uncover every detail and learn every lesson” from the terrorist strikes. The bill creates a 10-member independent panel for an 18-month inquiry into the attacks on Washington and New York that killed more than 3,000.

Debate about the commission has been marked by differences between the White House, Democrats and victims’ relatives over how far the probe should go and whether Bush himself should testify.

Kissinger’s appointment gives the commission instant respectability, and puts a White House ally in charge of an inquiry that has the potential to embarrass Bush.

Kissinger, 79, echoed the president in pledging to “go where the facts lead us.” He said he would accept no restrictions.

Later, Democratic congressional leaders named former Senate Majority Leader George Mitchell to be vice chairman of the panel. After leaving the Senate in 1995, Mitchell led the negotiations that produced the landmark Good Friday peace pact of 1998 for Northern Ireland.

The commission will build upon the work of congressional investigators who reported this year that clues to the hijackers’ plot were ignored or misunderstood.

Lawmakers have criticized the CIA for not tracking two al-Qaida operatives it learned of in early 2000. Those operatives were two of the five hijackers on the plane that crashed into the Pentagon.

Congressional investigators also noted poor communication between the FBI and CIA on terrorism matters, and questioned the State Department on visa programs that allowed all 19 hijackers to enter the country unchallenged.

“This commission will help me and future presidents to understand the methods of America’s enemies and the nature of the threats we face,” Bush said at a ceremony across the hall from the Oval Office.

The commission has a broad mandate to examine issues such as aviation security and border problems, along with intelligence.

While the president said lessons could be learned from Sept. 11, he seemed to put a greater emphasis on the panel determining methods and motives of terrorists who might strike in the future.

“Our goal is to take every measure that is necessary to gather information that is available and gain every advantage that is possible,” Bush said.

Democrats and some family members laid out goals that assume a more critical look at the government’s actions before Sept. 11.

Sen. Joseph Lieberman, D-Conn., said the inquiry must study why America’s “defenses failed.” He added: “Our goal is to know everything we possibly can know about the causes of Sept. 11.”

Beverly Eckert, a Stamford, Conn. resident whose husband perished in the World Trade Center attacks, said the government failed to “protect its citizens.”

After attending the ceremony, she said Bush and Kissinger seem committed to the inquiry but she’ll be “watching closely to make sure they do it right.”

It was Bush’s third major bill-signing in as many days and served as a holiday send-off for the president. He left afterward to spend the long Thanksgiving weekend at his Crawford, Texas, ranch.

Like the Homeland Security Department, the independent commission was an idea Bush came to support only after intense political pressure.

Kissinger, a pillar of the foreign policy community, was secretary of state and national security adviser for Presidents Nixon and Ford. One of the best-known secretaries of state, he was awarded the Nobel Peace Prize in 1973 for his efforts to end the Vietnam War _ but he also has been strongly criticized by some for his wartime service.

Lieberman, who pushed for the commission over Bush’s initial objections, called the appointment a good beginning and said he suspected that Kissinger did not want to end his career on a partisan note.

Kissinger, chairman of an international consulting firm that carries his name, has ties to the Bush family and has provided informal advice to the White House. He donated thousands of dollars to Republican candidates in the last two election cycles, though none to Bush himself.

The president signed the bill one day after the White House said Bush did not envision testifying to the panel, in part because there was no precedent for it.

However, President Reagan testified before a panel he appointed to investigate the Iran-Contra affair and Ford testified before a House subcommittee about his pardoning of Nixon.

Lieberman suggested he would seek Bush’s testimony.

“I would be surprised if this commission, in pursuit of the truth, the whole truth and nothing but the truth so help them God, did not want to speak with this president and high officials in this administration and previous administrations,” the Democrat said.