Washington ? A group of 26 former senior diplomats and military officials, many appointed to key positions by Republican Presidents Ronald Reagan and George H.W. Bush, plan to issue a joint statement this week arguing that President George W. Bush has damaged America’s national security and should be defeated in November.

The group, which calls itself Diplomats and Military Commanders for Change, will explicitly condemn Bush’s foreign policy and urge his defeat in November, according to several of those who signed the document.

“It is clear that the statement calls for the defeat of the administration,” said William C. Harrop, the ambassador to Israel under George H.W. Bush and one of the group’s principal organizers.

Those signing the document, which will be released Wednesday in Washington, include 20 former U.S. ambassadors, appointed by presidents of both parties, to countries from Israel and the former Soviet Union to Saudi Arabia and Mexico. Others are senior State Department officials from the Carter, Reagan and Clinton administrations and former career military leaders, including retired Gen. Joseph P. Hoar, who was commander in chief of the U.S. Central Command under the elder Bush. Hoar, who in his command post was responsible for the Middle East, has become a prominent critic of the war in Iraq.

Some of those signing the document — such as Hoar and former Air Force Chief of Staff Merrill A. McPeak — have already identified themselves as supporters of Sen. John Kerry, the presumptive Democratic presidential nominee. But most have not endorsed any candidate, according to the group. Also, it is unusual for so many high-level military and diplomatic alumni to issue such an overtly political message during a presidential campaign.

Bush camp response

A senior official at the Bush re-election campaign said he did not wish to comment on the statement until it was released.

But administration officials have emphatically rejected charges that Bush has isolated America in the world, pointing to the countries contributing troops in Iraq and such signs of support for the administration as the unanimous passage last week of the U.N. resolution authorizing the interim Iraqi government.

One senior Republican strategist familiar with White House thinking said he did not believe the group was sufficiently well-known to create significant political problems for the president. The strategist, who asked not to be named, also said it was making an argument growing increasingly obsolete as Bush relies more on the international community in Iraq.

President Bush, center, walks past the Bolling Air Force Base Little League Cardinals, from Washington, at the opening of the White House South Lawn T-Ball games. A group of 26 former senior diplomats and military officials plans to issue a joint statement this week arguing that Bush should be defeated in November.

“Their timing is a little off, particularly in the aftermath of the most recent U.N. resolution,” he said. “It seems to me this is a collection of resentments that have built up, but it would have been much more powerful months ago than now when even the president’s most disinterested critics would say we have taken a much more multilateral approach” in Iraq.

Years of work undone

But those signing the document say the recent signs of cooperation do not reverse a basic trend toward increasing isolation for the United States.

“We just felt things were so serious, that America’s leadership role in the world has been attenuated to such a terrible degree by both the style and the substance of the administration’s approach,” said Harrop, who earlier served as ambassador to four African countries under Presidents Carter and Reagan.

“A lot of people felt the work they had done over their lifetime in trying to build a situation in which the United States was respected and could lead the rest of the world was now undermined by this administration, by the arrogance, by the refusal to listen to others, the scorn for multilateral organizations,” Harrop said.

Jack F. Matlock, who was appointed by Reagan as ambassador to the Soviet Union and retained in the post by George H.W. Bush during the final years of the Cold War, expressed similar views.

“Ever since Franklin Roosevelt, the U.S. has built up alliances in order to amplify its own power,” he said. “But now we have alienated many of our closest allies, we have alienated their populations. We’ve all been increasingly appalled at how the relationships that we worked so hard to build up have simply been shattered by the current administration in the method it has gone about things.”