US Defense Secretary Robert Gates called for a cautious approach in changing the existing US policy on gays serving in the military.
"I believe this has to be done very, very carefully," Gates said, referring to the 'don't ask, don't tell' policy that President Barack Obama has vowed to repeal.
Under the policy, gays and lesbians can serve in the military, provided they do not reveal their sexual identity.
"The president has made it clear where he wants to go" with the law, Gates said, but he cautioned it was "a complex and difficult problem.
"There is a law. If the law changes so will our policies," added Gates during a visit to Carlisle, Pennsylvania, where he was to give a talk on his budget policies to the Army War College.
Gates emphasized that the US military was "under considerable strain right now" because of the wars in Iraq and Afghanistan.
"If we do go down that road, we have to do it in a way that mitigates any downsides, problems that might be associated with it," he warned.
Gates noted that it took five years for the law on ending racial segregation in the military, signed by former President Harry Truman in 1948, to come into force.
"I am not saying that is a model for this, but I believe this is something that needs to be done very, very carefully," Gates said, adding that he had already began discussing the subject with Obama and US Chairman of the Joint Chiefs of Staff Michael Mullen, the country's top military officer.
Since the policy was adopted in 1993, some 13,000 soldiers have been dismissed for mentioning their sexuality or after being cited, according to the Servicemembers Legal Defense Network, a rights group working for an end to discrimination in the military.
"I guess it's very difficult ... to get people to talk about it, you have to have almost a one on one private conversation," Gates later told reporters. "It's very difficult for people to speak in front of their peers about it."
Shortly after his inauguration in 1993, president Bill Clinton ordered the Pentagon to end discrimination based on sexual orientation during military recruitment.
The move was received very coolly by the majority of the US public and Clinton's Republican opposition.