WASHINGTON (Reuters) - The Pentagon will unveil steps next week that the military will take to lay the ground for a repeal of its “don’t ask, don’t tell” policy, which permits gays to serve in uniform as long they hide their sexual orientation, officials said on Thursday.

Defence Secretary Robert Gates and the chairman of the Joint Chiefs of Staff, Admiral Mike Mullen, will present an “implementation plan” to U.S. lawmakers next Tuesday, spelling out measures that the Pentagon will take internally before the White House and the Congress move to change the law.

In his first State of the Union speech on Wednesday, President Barack Obama called for ending the policy, saying: “This year, I will work with Congress and our military to finally repeal the law that denies gay Americans the right to serve the country they love because of who they are.”

Gates has voiced caution in the past against moving too quickly to repeal the Pentagon’s “don’t ask, don’t tell” policy, which began in the early 1990s.

Pentagon press secretary Geoff Morrell declined to comment on what steps the military would take, telling reporters: “The secretary and the chairman have been and continue to work on an implementation plan and will be able to share it with you early next week.”

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

Obama’s call drew fire from Senator John McCain, the senior Republican on the Senate Armed Services Committee.

“I believe it would be a mistake to repeal the policy,” McCain said. “This successful policy has been in effect for over 15 years and it is well understood and predominantly supported by our military at all levels.”

The Human Rights Campaign, the largest U.S. gay rights group, welcomed Obama’s move.

“Our country simply cannot afford this discriminatory law that hurts military readiness by denying patriotic men and women the opportunity to serve,” said the group’s president, Joe Solmonese.

The policy was signed into law in 1993 by then-President Bill Clinton, a Democrat, as a compromise after the military objected to his calls to open its doors to gays.

The policy stopped the government from asking recruits or anyone in the military if they were homosexual, provided they did not disclose their sexual orientation.

Critics charge that having gays openly serve in the military would undermine morale and discipline. Others reject such complaints and call the current policy unfair and unwise.