No US troops have been fired for being gay in the last month, the Pentagon has said.

Last month, defence secretary Robert Gates tightened the rules on dismissals, placing the power to sack out gay troops in the hands of just three officials.

Previously, hundreds of officers had the power to fire soldiers whose sexual orientation became known.

Pentagon spokeswoman Cynthia Smith told Associated Press that no discharges had been approved since October 21st. She could not give the total number of discharges for previous months.

Aaron Belkin, an expert on the law and the executive director of the Palm Center at the University of California, said that 428 gay and lesbian troops were honorably discharged under Don’t Ask, Don’t Tell in 2009.

He said: “Statistically, it would be extremely unlikely if we had a month in which there were no gay discharges. When you require a service secretary to sign off on a discharge, you are basically saying, ‘We don’t want any people in this category discharged unless there is an exceptional situation.’”

A Pentagon survey on the impact of lifting the ban is due to be released on November 30th. According to reports, it will show majority support among soldiers for repealing the 1993 law.

On Sunday, the chairman of the Joint Chiefs of Staff. Admiral Mike Mullen, said Congress should not wait to repeal the law and should move before the courts do.

He told ABC’s Christiane Amanpour: “The other piece that is out there that is very real is the courts are very active on this, and my concern is that at some point in time the courts could change this law and in that not give us the right amount of time to implement it.

“I think it’s much better done if it’s going to get done, it’s much better done through legislature than it is out of the courts.”

Earlier this month, the 9th US Circuit Court of Appeals ruled that Don’t Ask, Don’t Tell should stay in place indefinitely after a US district judge ended the ban.