The Pentagon conducted a year-long study of the law - known as Don't Ask, Don't Tell - which was introduced in 1993.

It allows homosexuals to join the military as long as they keep their sexuality a secret.

An executive summary of the report says: "While a repeal of Don't Ask Don't Tell will likely, in the short term, bring about some limited and isolated disruption to unit cohesion and retention, we do not believe this disruption will be widespread or long lasting."

The most powerful evidence gathered by the working group came from the survey results sent to 400,000 active duty and reserve service members and 150,000 spouses and family members.

A total of 115,052 people responded to the surveys, with 70% saying they thought repeal would have mixed, positive or no effect.

Ninety-two per cent of active duty or reserve service members said their experiences serving with co-workers they believed to be gay or lesbian were either "very good," "good," or "neither good nor poor".

But the survey does highlight resistance to overturn the ban.

General James Amos

US Marine Corps General James Amos has indicated his resistance

It is strongest among older servicemen, and in the Marines where 46% of whom believed repealing the law would have negative consequences.

The Marine Commandant, General James Amos, supports his men.

He told his confirmation hearing this September that such a move could damage unit cohesion at a time when America is fighting two wars.

All of America's Nato allies except Turkey allow gay service members. The UK ended its ban in 2000, while Israel started allowing openly gay recruits after 1993.

Among the countries who don't allow homosexuals to serve are Syria, Yemen, Pakistan, Iran and North Korea.

Defence Secretary Robert Gates ordered the review in February of this year, after President Barack Obama made in clear in his State of the Union address that he wanted to repeal Don't Ask Don't Tell.

Secretary Gates and Joint Chiefs Chairman Admiral Mike Mullen are expected to testify on the report in front of the House and Senate Armed Services Committees on Thursday and Friday.

A bill that included language to repeal Don't Ask Don't Tell passed in the House or Representatives this year but failed to pass in the Senate.

It's unclear whether or not Congress will vote on it again before the end of the lame duck session.