The Bush administration does not understand the world and remains unable to handle "in either style or substance" the responsibilities of global leadership, a group of 27 retired diplomats and military commanders charged yesterday.

"Our security has been weakened," the former ambassadors and four-star commanders said in a statement read to a crowded Washington news conference. "Never in the 21/4 centuries of our history has the United States been so isolated among the nations, so broadly feared and distrusted."

The statement fit onto a single page, but the sharp public criticism of President Bush was striking, coming from a bipartisan group of respected former officials united in anger about U.S. policy. The commentary emerges as public doubts about the Iraq invasion and Bush's handling of national security have risen.

The new group, which calls itself Diplomats and Military Commanders for Change, believes Bush should be defeated in November if the United States hopes to rebuild its credibility and strengthen valuable foreign alliances.

Secretary of State Colin L. Powell, speaking later in the day to al-Jazeera, rejected the criticism as a political act. He said the signers, most of whom he knows personally, "made it clear what they wish to see -- they wish to see President Bush not reelected."

"I do not believe that will be the judgment of the American people," Powell added.

"I disagree that the United States is so isolated, as they say," he told the Qatar-based satellite television network. "I mean, the president has gone to the United Nations repeatedly in order to gain the support of the international community. We are in Iraq with many other nations that are contributing troops. Are we isolated from the Brits, from the Poles, from the Romanians, from the Bulgarians, from the Danes, from the Norwegians?"

Among the retired officials signing the statement were Adm. William J. Crowe Jr., chairman of the Joint Chiefs of Staff under President Ronald Reagan and U.S. ambassador to the Court of St. James's under President Bill Clinton, and Marine Gen. Joseph P. Hoar, named by President George H.W. Bush to lead U.S. forces in the Middle East.

The participants also include a pair of former ambassadors to the Soviet Union, two former ambassadors to Israel, two former ambassadors to Pakistan and a former director of the CIA.

On a day when the independent commission investigating the Sept. 11, 2001, terrorist attacks said it found "no credible evidence" that Saddam Hussein worked with al Qaeda on any missions in the United States, the 27 signers accused the Bush administration of a "cynical campaign to persuade the public that Saddam Hussein was linked to al Qaeda and the attacks of Sept. 11."

The group said it did not coordinate its statement with the Democratic presidential campaign of Sen. John F. Kerry (Mass.), who shares many of its views. One signer, retired Gen. Merrill A. "Tony" McPeak, former U.S. Air Force chief of staff, described himself as a Kerry adviser.

McPeak was the Oregon chairman of Republican Robert J. Dole's presidential campaign in 1996, and he joined Veterans for Bush in 2000.

"This administration has gone away from me," McPeak told reporters at the National Press Club, "not vice versa."

The former officials said the administration "adopted an overbearing approach to America's role in the world, relying on military might and righteousness, insensitive to the concerns of traditional friends and allies, and disdainful of the United Nations. . . . Motivated more by ideology than by reasoned analysis, it struck out on its own."

Charles W. Freeman Jr., former U.S. ambassador to Saudi Arabia, cited a "post-9/11 atmosphere of hysteria."

"I think we will in time come to be very ashamed of this period in history," Freeman said, "and of the role some people in the administration played in setting the tone and setting the rules."

Donald F. McHenry, a former U.S. ambassador to the United Nations, answered a question about U.S. public diplomacy, a topic of special Bush administration focus, especially in the Muslim world.

"You can embark on all the public diplomacy you wish, but if there is no substance to the policy, it's very difficult to sell," he said.