Britain's Ministry of Defence it was unaware of the markings
Coded references to biblical passages are inscribed on gunsights widely used by the US and British military in Iraq and Afghanistan, it has emerged.
The markings include "2COR4:6" and "JN8:12", relating to verses in the books of II Corinthians and John.
Trijicon, the US-based manufacturer, was founded by a devout Christian, and says it runs to "Biblical standards".
But military officials in the US and UK have expressed concern over the way the markings will be perceived.
The company had been adding the references to its sights for many years, but the issue surfaced only recently when soldiers complained to an advocacy group, an ABC News investigation found.
Versions of Trijicon's Advanced Combat Optical Gunsight (Acog) are used by the US Special Operations Forces, the US Marine Corps and the US Army.
Britain's Ministry of Defence has just ordered 480 Acog sights for use on its new Sharpshooter rifles - to be used by troops in Afghanistan. Other versions of the Acog sight are "widely in service", the ministry says.
The inscriptions are subtle and appear in raised lettering at the end of the stock number.
John 8:12 reads: "When Jesus spoke again to the people, he said, 'I am the light of the world. Whoever follows me will never walk in darkness, but will have the light of life."
The nod to part of the second letter of Paul to the Corinthians, found on the company's Reflex sight, references the text: "For God, who said, 'Let light shine out of darkness,' made his light shine in our hearts to give us the light of the knowledge of the glory of God in the face of Christ."
An MoD spokesman told the BBC the ministry appreciated the biblical references could cause offence and was talking to its supplier, but was "not aware at the time of purchase that these markings had any broader significance".
The US Defense Department is a major customer of Trijicon's, signing deals for $66m (£40.8m) of the company's products in 2009 alone.
The US Marine Corps told the BBC they were "concerned with how this may be perceived" and were meeting with the company to "discuss future sight procurements".
The US Army said it was looking into any potential policy violation.
The issue has been thrust into the spotlight by the US Military Religious Freedom Foundation (MRFF) - an advocacy group that seeks to preserve the separation of church and state in the military.
On 14 January, the MRFF received an e-mail, purportedly from a Muslim US Army infantryman, complaining about the markings.
"Many soldiers know of them and are very confused as to why they are there and what it is supposed to mean."
The email adds: "Everyone is worried that if they were captured in combat that the enemy would use the Bible quotes against them in captivity or some other form of propaganda."
MRFF president Mikey Weinstein says the inscriptions could give the Taliban and other enemy forces a propaganda tool.
"I don't have to wonder for a nanosecond how the American public would react if citations from the Koran were being inscribed onto these US armed forces gunsights instead of New Testament citations," he said.
A Trijicon spokesman told the BBC the company "has been working to provide America's military men and women with high quality, innovative sighting systems for the weapons they use".
"Our effort is simple and straightforward: to help our servicemen and women win the war on terror and come home safe to their families.
"As part of our faith and our belief in service to our country, Trijicon has put scripture references on our products for more than two decades.
"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," the spokesman added.
The company states on its website: "We believe that America is great when its people are good. This goodness has been based on biblical standards throughout our history and we will strive to follow those morals."