Washington ? The Pentagon made it harder to boot gays out of the military Thursday, acting on its own while Congress considers President Barack Obama’s goal of lifting the ban on gays serving openly.

Defense Secretary Robert Gates approved new rules to ease enforcement of the 1993 congressional ban, saying the changes reflect “common sense and common decency.”

The new guidelines, meant to keep the “don’t ask, don’t tell” law from being used to launch witch hunts or settle grudges, represent the first significant step by the administration to address what Obama calls an injustice.

The changes would tighten the rules for evidence when someone reports that a soldier is gay and put higher-ranking officers in charge of dismissal proceedings.

An estimated 13,000 people have been discharged under the law.

Although most of the dismissals have been the result of gay service members outing themselves, advocates for repeal of the law say it has been used to drum out capable soldiers who never made their sexuality an issue.

Gates said the changes, effective immediately, are “an important improvement in the way the law is put into practice,” short of repealing it. The changes give “a greater measure of common sense and common decency for handling what are complex and difficult issues for all involved,” he told a Pentagon news conference.

Gay rights groups have long advocated for these changes, contending that the rules unfairly kept gay troops from seeking medical help or reporting domestic abuse for fear of being exposed and expelled.

Mike Almy, a former Air Force major who was fired in 2006 for being gay, says he believes he would have kept his job had these new guidelines been in effect at the time.

Almy was dismissed after a routine computer search turned up personal e-mails he wrote while deployed in Iraq.

After the e-mails were given to his commander, he was handed discharge papers marked “homosexual admission” as the reason for leaving the service.

“It’s going to stop the most vile aspects of the law,” Almy said of the rules. But “it’s not a substitute for full repeal, which has to come from Congress.”

Gates and Adm. Mike Mullen, Chairman of the Joint Chiefs of Staff, support a repeal of the law but want to move slowly to ensure the changes won’t hurt the military’s effectiveness. Gates ordered a review, due Dec. 1, on how the military would implement a repeal, should Congress change the law.

“Doing it hastily is very risky,” Gates said Thursday.

The changes he announced take effect immediately and apply to current as well as future cases. Pentagon officials said they were unsure how many people the new rules might affect.

Among the new guidelines is a requirement that the firing of gay enlisted personnel be done by an officer at a rank at least equivalent to a one-star general.

The guidelines also say that information supplied by third parties should be given under oath and that testimony from a person who might be seeking revenge shouldn’t be allowed. No longer admissible in dismissal cases is information given in confidence to lawyers, clergy, psychotherapists or medical professionals.

As for outright repeal of the ban, it is unclear whether there is enough support in Congress. Conservative Democrats have joined Republicans in warning against lifting the ban at a time of two wars, and even the go-slow effort has strong critics in and outside the military.

In a defiant letter in the military newspaper “Stars and Stripes,” a three-star Army general recently called efforts to repeal the ban ill advised and urged troops and their families to speak up.

“Now is the time to write your elected officials and chain of command and express your views,” Lt. Gen. Benjamin Mixon, who commands Army troops in the Pacific theater, wrote this month.

In a rare public admonishment of another senior-ranking officer, Mullen said Thursday that it was inappropriate for an officer — particularly of Mixon’s rank and stature — to publicly challenge the president’s priorities.

“The answer is not advocacy. It is, in fact, to vote with your feet,” Mullen said at the Pentagon.