US Marines have begun training in preparation to accept openly gay troops.

Before President Obama signed an order to repeal the 17-year-old ban, there was concern that the Marines in particular would react badly to serving alongside out gay colleagues.

A Pentagon survey carried out last year showed that nearly 60 per cent of troops in the most dangerous roles – in the Marines and combat units – said repeal would be damaging.

General James Amos, commandant of the Marine Corps, said at the time that gay servicemembers might cause a “distraction” that could result in increased injuries and deaths.

According to AP, training materials ask Marines to consider scenarios such as seeing a colleague in a gay bar or hearing locker-room jokes aimed at gay colleagues.

While Marines will not be expected to change their views, the materials say they must follow orders.

“You remain obligated to follow orders that involve interaction with others who are gay or lesbian, even if an unwillingness to do so is based on strong, sincerely held moral or religious beliefs,” the training material states.

Testifying before a Senate Armed Forces hearing earlier this month, Gen Amos said: “We’ve not seen issues. There’s not been anxiety over [out gay soldiers] from the forces in the field … there hasn’t been pushback.”

It is expected that gay soldiers will be permitted to come out at some point during the summer.

The ban will not be lifted until military chiefs have certified that repealing the law will not harm military readiness. Following this, 60 days must pass.