The British Ministry of Defense meanwhile announced it had placed an order for 400 of the gunsights with Trijicon but added it had not been aware of the significance of the inscriptions, in a decision criticized by the opposition Liberal Democrat party.
The Muslim Public Affairs Council (MPAC) called on US Defense Secretary Robert Gates to immediately withdraw from combat use equipment found to have inscriptions of Biblical references after it emerged that Trijicon has contracts to supply over 800,000 of the sights to the US military.
The Pentagon sought to defuse the brewing controversy, saying it was "disturbed" by the reports.
"If determined to be true, this is clearly inappropriate and we are looking into possible remedies," Commander Darryn James, a Pentagon spokesman, told AFP.
The codes were used as "part of our faith and our belief in service to our country," Trijicon said.
"As long as we have men and women in danger, we will continue to do everything we can to provide them with both state-of-the-art technology and the never-ending support and prayers of a grateful nation," a company spokesman said on condition of anonymity.
The move appeared to be a direct violation of a US Central Command general order issued after the 2003 US-led invasion of Iraq that strictly prohibits "proselytizing of any religion, faith or practice."
A whistleblower group that first alerted ABC News to the issue this week warned the practice was putting troops in harm's way by raising fears of Christian proselytizing in Muslim-majority nations home to militants resentful of US military presence.
"This is the worst type of emboldenment of the enemy that you can imagine," Military Religious Freedom Foundation founder and president Michael "Mikey" Weinstein said in an interview.
Weinstein, a former White House legal counsel in Ronald Reagan's administration, said his group would submit a filing in US federal court in Kansas City, Missouri by February 4 in a related case.
"Having Biblical references on military equipment violates the basic ideals and values our country was founded upon," MPAC Washington director Haris Tarin said in a statement.
"Worse still, it provides propaganda ammo to extremists who claim there is a 'Crusader war against Islam' by the United States," he added.
The shocking revelation raises fresh fears of Christian fundamentalism seeping through the US military's ranks.
"It's got to stop. It's wrong on a million levels," said Weinstein. "This is massively endangering the lives and well-being of our members of the military."
His foundation, he added, represents nearly 16,000 troops, the bulk of them Christians.
A Muslim-American soldier, who declined to be named due to fears of persecution, said he was "ashamed" and "horrified" by the writings on the gunsights of weapons he used during deployments in Iraq and Afghanistan.
"There are many other soldiers who feel as I do. Many are Protestant and Catholic and they fear reprisal just as much as I do for trying to stand up to the Christian bullies in uniform who outrank us," he said in a letter dated January 14 and addressed to Weinstein and his foundation.
According to photographs seen by AFP, the coded inscriptions include JN8:12, an apparent reference to John 8:12: "Then spake Jesus again unto them, saying, I am the light of the world: he that followeth me shall not walk in darkness, but shall have the light of life."
Trijicon, a defense contractor founded by devout Christian Glyn Bindon, vows on its website to follow "biblical standards" it says make America great.
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