WASHINGTON (Reuters) - The retired general whose opposition deflected the last serious bid to let homosexuals serve openly in the U.S. military, Colin Powell, reversed himself on Wednesday and backed President Barack Obama’s move to repeal the restrictions on gays.

Powell’s intervention followed by one day an announcement of support for Obama’s proposal by Pentagon chief Robert Gates and a strong appeal to let gays serve openly by the nation’s top uniformed officer, Admiral Michael Mullen.

Gates and Mullen spent part of Wednesday trying to defuse opposition in Congress to the move.

Mullen, who says allowing gays to serve openly is “an issue of integrity,” is chairman of the Joint Chiefs of Staff, the job Powell held in 1993, when he resisted President Clinton’s efforts to lift the ban on gays in the U.S. armed forces.

That year, Congress struck a compromise “don’t ask, don’t tell” policy allowing gays to serve in the military only if they remained silent about their homosexuality. This is what Obama wants to change, and Powell said on Wednesday he now favored changing it too.

“In the almost 17 years since the ‘don’t ask, don’t tell’ legislation was passed, attitudes and circumstances have changed,” Powell said in a statement.

“I fully support the new approach presented ... this week by Secretary of Defense (Robert) Gates and Admiral Mullen.”

Powell’s endorsement could give a boost to Obama’s efforts to lift the current restrictions. Obama has come under pressure from some gay activists who backed him as a presidential candidate but were disappointed that he had not acted sooner on major gay rights issues.

But ultimately the policy can only be changed by Congress, and some lawmakers in both parties strongly oppose Obama’s move, saying it could hurt morale and discipline. Gates and Mullen on Wednesday assured them they would only move forward on the plan with plenty of consultation within the ranks.

Gates, who once ran the U.S. Central Intelligence Agency, told lawmakers in the House Armed Services Committee that he had learned from experience it was “stupid to try to impose a policy from the top without any regard for the views of the people who were going to be affected.”

He and Mullen said consultation with ordinary servicemembers was part of the review they had ordered to examine how the change might affect unit cohesion, recruitment and retention, as well as the possibility of extending marriage and bereavement benefits to the partners of gay soldiers.

They also denied that they were trying to delay the policy by giving the review up to a year to be completed.

“I think rushing into it, mandating it by fiat with a very short timer on it, would be a very serious mistake,” Gates said.

But the Armed Services Committee’s top Republican, Representative Howard McKeon, was critical. He noted that Gates and Mullen made it clear a day earlier that they were “ready to implement a repeal” before the consultation took place.

“It seems that your path places the cart before the horse,” McKeon said.

The policy bans openly gay people from serving but prohibits military officials from initiating inquiries on sexual orientation when soldiers are abiding by the rules.