A group of senior former US government officials will release a statement later this week condemning President George W Bush's foreign policy.
The statement could hurt Bush in the election campaign
The group call themselves Diplomats and Military Commanders for Change.
They say Mr Bush's policies have made the US more isolated and less safe, and damaged its standing in the world.
The BBC's Jon Leyne in Washington says former officials have criticised Mr Bush before, but this time the critics are especially well-respected.
They include William Crowe, who as chairman of the joint chiefs of staff, was America's top military officer and Admiral Stansfield Turner, a former director of the CIA.
The statement follows criticism last month by 53 former diplomats who accused the administration of undermining US credibility in the Arab world with its strong support for Israeli Prime Minister Ariel Sharon.
The British government has also come under fire, with 52 former officials attacking Prime Minister Tony Blair's support for Washington over Iraq and the Israeli-Palestinian conflict.
Those signing the statement say they believe the Bush administration has made the international outlook more unstable and dangerous.
Phyllis Oakley, the former deputy state department spokesperson under President Reagan, told the BBC World Service's World Today programme that Mr Bush's Iraq policy had played a big part in their decision to publicise their concerns.
DIPLOMATS AND MILITARY COMMANDERS FOR CHANGE
William C Harrop
Ambassador to Israel under Bush Sr
Gen Joseph P Hoar
Commander in chief of US Central Command under Bush Sr; supports John Kerr
Merrill A McPeak
Former Air Force chief of staff; supports Kerry
Jack F Matlock
Ambassador to the USSR under Reagan and Bush Sr
Adm William J Crowe
Chairman of the Joint Chiefs of Staff under Reagan and ambassador to UK under Clinton; has endorsed Kerry
Adm Stansfield Turner
CIA director under Carter; has endorsed Kerry
"But it goes beyond that to the whole thrust of his posture for the US and the world - to move away from the international structures that have been painstakingly built up over the years, away from our work with allies," she said.
Ms Oakley said it was a "dangerous posture" for the US to act as the "unilateral, sole superpower" that could impose its will on others.
"We cannot go it alone," she said.
In their criticisms of US policy on Iraq, the signatories say that all the assumptions made by the administration before the invasion have been proved wrong.
"It's a plea with the president to more urgently seek multilateral support for what we're doing in Iraq, to go back and forth in strengthening the alliances we've traditionally worked with," Admiral Crowe told the BBC.
The group is made up of both Democrats and Republicans.
Known critics of the administration were deliberately excluded.
However, several individual signatories have said they will back Mr Bush's Democrat challenger John Kerry and others say that the document is in effect calling for the president's removal.
"It is clear that the statement calls for the defeat of the administration," Mr Harrop said.
But supporters of the administration said the former officials who signed the letter were simply trying to hide the inadequacy of their own policies.
"Largely, they are people who were in senior official capacities before 9/11. They are people who are responsible for the policies prior to 9/11. Those policies I think, failed spectacularly on 9/11," Cliff May, president of the conservative Foundation for the Defense of Democracies, told the BBC.
"It seems that these folks feel that those policies in place before 9/11 were perfectly fine. Nevertheless, these are what some people might describe as 9/10 people, they want to continue with the failed policies and they don't want to change those policies despite their failures."