Gun sights with biblical inscriptions will not be withdrawn from New Zealand soldiers in Afghanistan but New Zealand defence bosses want them cleaned up.

The New Zealand soldiers were issued with Trijicon advanced combat optical gun sights but defence officials have only just learned they had a biblical inscription put on them by the American manufacturer, Trijicon Incorporated.

The sights, dubbed "Jesus sights" by overseas media, were also issued to American troops, and troops from other countries, but the news outraged Muslim groups, who said it could provide propaganda material for extremists claiming there was a "crusader war against Islam" by the United States.

The New Zealand Army bought about 260 of the sights in 2004 and would not say how many were in Afghanistan, although it is believed they were fitted to some weapons issued to New Zealand SAS troops.

One of the inscriptions was 2COR4:6, which is an apparent reference to Second Corinthians 4:6 of the New Testament.

The passage reads: "For God, who commanded the light to shine out of darkness, hath shined in our hearts, to give the light of the knowledge of the glory of God in the face of Jesus Christ."

Another, JN8:12, referred to John 8:12, and read: "Whoever follows me will never walk in darkness, but will have the light of life."

Army spokesman Major Kristian Dunne said they were talking with the manufacturer about ways of removing the references, which were stamped on the sights as part of the serial number.

He said it was not just a matter of grinding the numbers off.

"We just need to make sure we don't damage them because they are a good bit of kit."

He said they did not want to do anything which affected the performance of the sights.

The army knew nothing of the inscription until the news broke overseas recently.

Maj Dunne said the numbers were faint and looked as if they were part of the serial number.

In America the Muslim Public Affairs Council demanded US Defence Secretary Robert Gates immediately withdraw the sights from combat use.

The US military bought up to 800,000 of the sights.

Trijicon said in a statement "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."

Prime Minister John Key said the Government was not aware the gun sights had biblical inscriptions when the New Zealand Defence Force purchased them.

"Now we are in discussions with the company in the United States who will ensure the inscriptions are removed, and we wouldn't want them on future sights.

"We are going to continue to buy that product because it's the best product in the world, and provides the best level of safety and security for our defence forces."

Mr Key said the inscriptions were inappropriate and the New Zealand Defence Force was entitled to know about them.