WASHINGTON — The White House weighed a quick appeal of a judge’s order abruptly allowing gays to serve openly in the military as Pentagon chief Robert Gates warned on Wednesday of “enormous consequences” for men and women in uniform if the ruling stands.

A day after the federal judge in California ordered the Pentagon to cease enforcement of the “don’t ask, don’t tell” law, Gates told reporters traveling with him in Europe that repealing the law should be a question for Congress — and only after the Pentagon completes its study of the issue.

Allowing gays to serve openly “is an action that requires careful preparation and a lot of training,” Gates said. “It has enormous consequences for our troops.”

In Tuesday’s ruling, U.S. District Judge Virginia Phillips ordered the military “immediately to suspend and discontinue any investigation” or other proceeding to dismiss gay service members. The 1993 law says gays may serve in the military but only if they keep secret their sexual orientation.

Phillips wrote that the law “infringes the fundamental rights” of current and prospective service members.

Gay rights advocates cautioned gay service members to avoid revealing their sexuality for fear that the Phillips ruling could be tossed out on appeal and they would be left open to being discharged.

Defense Department officials would not say what was happening to current discharge cases, or even confirm how many pending cases there might be. A Pentagon spokesman, Col. David Lapan, said no written guidance had been issued to commanders on how to deal with the court order.

An Air Force officer and co-founder of a gay service member support group called OutServe said Wednesday he will continue using a pseudonym out of concern that he could still be discharged.

“Can I come out right now and be OK? And if I made a statement would it be held against me?” asked the officer, who calls himself JD Smith and said he is an Air Force Academy graduate. He said service members are hoping the Pentagon will clarify the meaning of the court ruling.

Warren Arbury of Savannah, Ga., said he’d love to re-enlist in the Army two years after being discharged in the middle of a tour in Iraq. But he’s being cautious and patient.

“I think it’s still way too soon,” said 28-year-old Arbury, now a university student. “If I was to hear news that automatically everything would be reinstated, I’d be the first one in the door.”

Arbury said he wants to know more about how the military would reintegrate gay ex-soldiers: “If I go back in I want to know, Do I get my rank back? Do I get any damages or compensation?”

The uncertainty extended overseas. When asked by a reporter whether the ruling had had any impact yet, a two-star U.S. Army commander in eastern Afghanistan suggested he was unsure anything would change and said it was unlikely that his soldiers even knew about the court order.

“If that law is changed, they’ll abide by the law,” but “that’s probably the farthest thing from their mind” as they fight, said Maj. Gen. John Campbell, commander of the 101st Airborne Division.

The Justice Department is considering whether to appeal the Phillips ruling, and its first response may well be another trip to the judge’s courtroom in Riverside, Calif., to seek a stay, or temporary freeze. If Phillips turns down the request, the Justice Department probably would then turn to the federal appeals court in California.

If the government does appeal, that would put the Obama administration in the position of continuing to defend a law it opposes.

White House press secretary Robert Gibbs said time is running out for the ban on gays serving openly.

“This is a policy that is going to end,” he said.

Gates, who supports lifting the ban once the Pentagon puts in place a plan for minimizing disruptions, said that besides developing new training for troops, regulations will have to be revised.

Gates and Adm. Mike Mullen, chairman of the Joint Chiefs of Staff, face disagreement by some senior general officers on whether lifting the ban would cause serious disruption at a time when troops are fighting in Afghanistan and winding down a long war in Iraq.

The incoming Marine commandant, Gen. James Amos, and his predecessor, Gen. James Conway, both have told Congress that they think most Marines would be uncomfortable with the change and that the current policy works.

In part to resolve the question of how the troops feel, Gates has ordered a study due Dec. 1 that includes a survey of troops and their families.

Gates has said the purpose isn’t to determine whether to change the “don’t ask, don’t tell” law, which he says is probably inevitable, but to determine how to end the policy without causing serious disruption.

Cultural values in the U.S. have shifted since the law was passed, yet there remains a powerful rhetorical weapon for opponents of lifting the ban — fear that it would weaken a military at war.

Family Research Council President Tony Perkins accused Phillips of “playing politics” with national defense.

“Once again, an activist federal judge is using the military to advance a liberal social agenda, disregarding the views of all four military service chiefs and the constitutional role of Congress,” he said.

Perkins urged the Justice Department “to fulfill its obligation to defend the law vigorously through the appeals process.”

President Barack Obama worked with Democrats to write a bill that would have lifted the ban, pending completion of the Defense Department review and certification from the military that troop morale wouldn’t suffer. That legislation passed the House but was blocked in the Senate by Republicans.

Democrats could revive the legislation in Congress’ lame-duck session after the midterm election.

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Anne Gearan reported from Brussels, Belgium. Associated Press writers Anne Flaherty and Robert Burns in Washington and Brian Witte in Annapolis, Md., contributed to this report.