US service staff can be dismissed if they reveal they are gay
The Pentagon has issued rules making it more difficult for gays to be dismissed from the US military.
New measures include increasing the rank at which officers could initiate investigations and tougher requirements for evidence used against homosexuals.
The changes are a matter of "common sense and common decency", Defence Secretary Robert Gates said.
Last month, the top US commander said openly gay people should be allowed to serve in the US military.
To limit expulsions of servicemen and women denounced by third parties, the measures require their information be given under oath.
Only higher-ranking officers will be allowed to initiate and oversee discharge cases.
And the use of "overheard statements and hearsay" will also be discouraged.
"I believe these changes represent an important improvement, in the way the current law is put into practice, above all by providing a greater measure of common sense and common decency, to a process for handling what are difficult and complex issues for all involved," Mr Gates said.
The changes take effect immediately, he added.
The move is an interim measure, while Congress debates the repeal of the existing policy - known as "don't ask, don't tell" - which says gays can serve in the military as long as their sexuality remains secret.
President Barack Obama has pledged to repeal the ban.
Under the law passed by Congress in 1993, engaging in homosexual conduct - even if the person concerned does not tell anyone - can be enough to qualify a person for dismissal.
It was introduced as a compromise between then-President Bill Clinton's desire to lift the ban totally, and concerns from Congress and the military that lifting it would be disruptive.
Recent figures from the Pentagon show that 428 service members were dismissed for being openly gay in 2009, down from 619 dismissed in 2008.
The number is by far the lowest since 1997, when 997 service members were dismissed.
Overall, more than 10,900 troops have been dismissed under the policy.