The Marines are the faction of the US military most opposed to lifting the ban on out gay troops, reports say.

The Pentagon has been surveying troops on the impact of lifting the ban and the full survey is to be released this week.

The Washington Post reports that around 70 per cent of troops think that changing the law to allow gay troops to serve openly would be good, mixed or not have much effect.

But the newspaper reported that Marines were found to be the most opposed.

There are 200,000 Marines and they are said to be the youngest and most close-knit group in the military. They also have higher casualty rates as they tend to be the first into combat situations.

In October, the the retiring commandant of the Marine Corps said that almost all Marines would be unhappy about serving with out gay colleagues.

Gen. James Conway told Fox News that “90 to 95 per cent of the Marines” he had informally surveyed said they had concerns about the consequences of allowing gay men and lesbians to serve openly.

The US Senate will vote again on whether to repeal the 1993 policy in the next few weeks.

A measure to repeal the policy is attached to the Defence Authorisation Bill. It passed the House in the summer but a vote in the Senate was blocked last month by Republicans.

It is unclear whether there is enough support to pass the repeal measure.