The group, which calls itself Diplomats and Military Commanders for Change, does not explicitly endorse Democrat John Kerry for president in its campaign, which will start officially Wednesday at a Washington news conference.
Among the group are 20 ambassadors, appointed by both Democratic and Republican presidents, other former State Department officials and military leaders whose careers span three decades.
Prominent members include retired Marine Gen. Joseph P. Hoar, commander of U.S. forces in the Middle East during the administration of Bush's father; retired Adm. William J. Crowe Jr., ambassador to Britain under President Clinton and chairman of the Joint Chiefs of Staff under President Reagan; and Jack F. Matlock Jr., a member of the National Security Council under Reagan and ambassador to the Soviet Union from 1987 to 1991.
The White House referred calls for comment to the Bush-Cheney campaign. Campaign spokesmen were not immediately available.
"We agreed that we had just lost confidence in the ability of the Bush administration to advocate for American interests or to provide the kind of leadership that we think is essential," said William C. Harrop, the first President Bush's ambassador to Israel, and earlier to four African countries.
"The group does not endorse Kerry, although it more or less goes without saying in the statement," said Harrop.
Harrop said he listed himself as an independent for years for career purposes but usually has voted Republican.
The former ambassador said diplomats and military officials normally avoid making political statements, especially in an election year.
"Some of us are not that comfortable with it, but we just feel very strongly that the country needs new leadership," Harrop said.
He said the group was disillusioned by Bush's handling of the war in Iraq and a list of other subjects, including the Middle East, environmental conservation, AIDS policy, ethnic and religious conflict and weapons proliferation.