President Bush will move fast to find a replacement for Henry Kissinger, who was propelled into the public eye during the Watergate scandal in the Nixon's administration, as chairman of a commission investigating the Sept. 11 terrorist attacks.

The former secretary of state abruptly resigned Friday because of conflict-of-interest concerns.

"His chairmanship would have provided the insights and analysis the government needs to understand the methods of our enemies and the nature of the threats we face," Bush said. "My administration will work quickly to select a new chairman whose mission will be to uncover every detail and learn every lesson of Sept. 11, even as we act on what we have learned so far to better protect and defend America."

Kissinger's resignation Friday came two weeks after his appointment and two days after the panel's vice chairman, former Sen. George Mitchell, D-Maine, stepped down. The twin resignations came as the commission hoped to begin its work next month and after disputes about its organization and its authority to issue subpoenas.

The 10-member commission will investigate events surrounding the attacks, examining issues including aviation security, immigration and U.S. diplomacy. It will build on a congressional inquiry, completed this week, into intelligence failures.

Kissinger's resignation came amid concerns of possible conflicts of interests involving his business clients and demands by some Democratic lawmakers that he make public the names of all of his clients. The White House had argued he wasn't required to do this because the chairmanship was an unpaid position.

Kissinger's appointment last month revived memories over his contentious service in the Nixon administration and his role in the war in Vietnam.

In a letter to Bush, Kissinger said he was willing to submit "all relevant financial information" to the White House and to an independent review but said he feared critics would demand he liquidate his international consulting firm, Kissinger Associates.

Kissinger's resignation came one day after he tried to assure Sept. 11 victims' relatives that his business interests would not conflict with his duties as chairman. He proposed a plan where he would reveal his clients to a third party chosen by the families who would not to make the names public.

Kissinger's move apparently triggered by a legal opinion from Republicans and Democrats on the Senate Ethics Committee, reported The New York Times on Saturday. The opinion was that all members of the commission would have to comply with Congressional financial disclosure requirements.

A friend of Kissinger told the Times that he had accepted the job in the spirit of public service and was unable to say no to the president. But when he realized his client list would become a such an issue and after various groups demanded the disclosure, Kissinger was forced to decide between breaking confidentiality agreements he has signed with his clients and his new job.

Kissinger's friend said there were "no deep dark secrets" on the client list, with no clients in the Middle East or in government.

Sen. Harry Reid of Nevada, the Senate Democratic whip, said it wasn't surprising someone with global ties such as Kissinger would eventually be forced to make such a decision when joining a panel looking into the conduct of foreign countries and domestic intelligence agencies.

"There were too many conflicts of interest for him to lead this task," Reid, chairman of the Ethics Committee, told the Times. "I knew he would never disclose that information. Now the country and the families deserve someone who won't be afraid to lead this commission."

Reid also criticized the White House for trying so hard to protect Kissinger's privacy.

"The pressure put on the Ethics Committee by the White House was really untoward," he said. "They were calling and berating our staff, saying he didn't have to file because he worked for the executive branch. I mean, come on. What were they trying to hide? Finally he realized he couldn't hide it anymore."

Former Rep. Lee Hamilton, D-Ind., who replaced Mitchell as vice chairman of the commission and is one of the Democrats' picks for the new chair, on Friday released a statement on the disclosure requirements.

"The Democratic members of the National Commission on Terrorist Attacks Upon the United States have examined the Senate Ethics Committee's interpretation concerning disclosure requirements for commission members," it read. "All five Democratic members support complete disclosure and we will each comply fully with the requirements as set forth under the Ethics in Government Act."

On Wednesday, Mitchell, the former Democratic senator from Maine, submitted his resignation because he said the job would conflict with his responsibilities to his law firm.

The resignations were greeted with favor by some relatives of victims of the Sept. 11 attacks.

Kristen Breitweiser, a leader of September 11th Advocates, said departure of Kissinger and Mitchell "reaffirms my belief that the commission needs to be pure, transparent and purely independent."

Stephen Push of Families of Sept. 11 said the resignation gives Bush "a second chance to appoint someone who will be a thorough and competent investigator."

The relatives' groups have been skeptical about whether Bush wants a full investigation of the attacks, with a potentially embarrassing report due less than six months before the 2004 election.

The commission already has become bogged down over disputes about its makeup -- five Republicans and five Democrats with the chairman named by Bush -- and how many votes should be required to issue subpoenas. The White House insisted at least a majority of six votes be required. That would prevent the five Democrats from issuing subpoenas on their own.

Republicans have yet to choose four of their five members.

In addition to Bush, who will select the new chairman, the GOP leaders of both the House and Senate each must pick two members.

Senate GOP leader Trent Lott of Mississippi already has selected former Sen. Slade Gorton, R-Wash., but has not announced his second choice. House Majority Leader Dennis Hastert, R-Ill., has yet to name his two selections, but is believed to be considering former U.S. Trade Representative Carla Hills and former Illinois Gov. Jim Thompson.

Democrats have named five members, including Hamilton.

The Associated Press contributed to this report.