A civil rights watchdog group called the Military Religious Freedom Foundation (MRFF) is demanding that the Marine Corps University in Virginia cancel the National Day of Prayer event, saying it's a violation of the Establishment Clause.

"This absurdly named organisation has nothing to do with religious freedom in the military and is actually on a campaign to remove religious freedom from the military," Matthew Clark of the American Center for Law and Justice (ACLJ) told CBN News.

The ACLJ sent a letter to Brig. Gen. Helen Pratt, university president, requesting her to reject the group's demands.

It said that the MRFF is also threatening to file complaints against Pratt for allowing a military chaplain to invite soldiers in training to an optional prayer service.

The move, the ACLJ said, is "dishonoring and legally wrong."

In its letter to Pratt, ACLJ said MRFF's Mikey "Weinstein's rhetorical attacks, though predominantly aimed at Christians, are not limited solely to Christians. For example, he has readily attacked Jews with whom he disagrees as well."

ACLJ Chief Counsel Jay Sekulow said when MRFF tried to court martial another general for participating in last year's National Day of Prayer, ACLJ fought back and won.

MRFF forced three Veterans Affairs hospitals and a military base to remove the Bible from "Missing Man" displays, which recognise MIA and POW soldiers.

Clark said MRFF's goal to remove every semblance of religion in the military cannot be allowed to happen, saying that "we sent off letters to the VA and to several of these military installations that have caved to the anti-Christian attacks."

The ACLJ is hoping that it can get some of the decisions reversed. It said there's no constitutional violation in honouring the faith of men and women in the military.

It told Pratt in the letter that "as a commander, you are the person responsible for the spiritual welfare of your command, not the chaplain."

It said holding periodic, voluntary prayer breakfasts is a way of meeting the spiritual needs of military personnel.