U.S. Defence Secretary Robert Gates testifies on Capitol Hill in Washington on Tuesday before a Senate armed services committee hearing. U.S. Defence Secretary Robert Gates testifies on Capitol Hill in Washington on Tuesday before a Senate armed services committee hearing. (Manuel Balce Ceneta/Associated Press)

The U.S. military has begun the reversal of a controversial 16-year-old law that bans openly gay men and women from serving in its ranks.

At a hearing in Washington, D.C., on Tuesday morning, U.S. Defence Secretary Robert Gates tapped his chief legal adviser and a four-star army general to lead a landmark study on how the military would lift its ban, known commonly as "Don't Ask, Don't Tell."

Pentagon general counsel Jeh Johnson and Gen. Carter Ham, who leads army forces in Europe, will serve as co-chairs of the yearlong study into how the ban can repealed without causing a major upheaval to the fighting forces.

Gates made the announcement in an appearance on Capitol Hill before the Senate armed services committee. It marks a measured step toward President Barack Obama's goal of eliminating the military's policy against gays.

Admiral Mike Mullen, chairman of the Joint Chiefs of Staff, also made an impassioned plea for allowing gays to serve openly in uniform, telling the Senate committee it is wrong to force people to "lie about who they are in order to defend their fellow citizens."

The law, passed in 1993 as part of the National Defence Authorization Act, says "homosexual conduct" is grounds for dismissal from the military. That includes "homosexual acts, or a homosexual marriage or attempted marriage," as well as any statements made that might indicate a propensity to engage in homosexual acts.

The regulations have affected an estimated 14,000 servicemen and servicewomen, including David Hall, a former sergeant in the U.S. air force who claims he was turfed after five years of service.

"It was very disappointing … to know that the only reason that I didn't get to become a pilot was just because of the fact that I was gay," Hall said. "It's the only federal law that allows the government … that specifically says the government's going to discriminate against a class of people."

In his State of the Union address on Jan. 27 Obama vowed to "work with Congress and [the] military to finally repeal the law that denies gay Americans the right to serve the country they love because of who they are.

"It's the right thing to do," Obama said, to great applause.

Policy 'has been effective'

But at Tuesday's committee hearing, it was clear not everybody agrees with him.

Sen. John McCain, the ranking Republican on the panel, publicly bristled at the Pentagon's decision to do the study, saying he is "deeply disappointed" and calling the assessment "clearly biased" because it presumes the law should be changed.

"Has this policy been ideal? No, it has not," McCain said. "But it has been effective."

Several other Republicans sided with McCain, warning Mullen and Gates not to pursue a change at a time when the United States is fighting two wars in Iraq and Afghanistan and facing a continuing threat of terrorism. Democrats said they would back a change in policy.

Senator Carl Levin, a Democrat from Michigan, and chairman of the committee, said a repeal of the law might be slipped into a broader military policy bill that authorizes defence spending.

Democratic Senator Mark Udall said his Colorado constituents pride themselves on allowing others to live and let live.

"You don't have to be straight to shoot straight," said Udall, quoting libertarian Barry Goldwater.

Gates suggested that lawmakers keep the intensity of debate in check until the military can get a better handle on how to proceed.

With files from The Associated Press