"Get the hound of heaven after them, so we get them into the kingdom. That's what we do, that's our business."
Admiral Mike Mullen, the Chairman of the Joint Chiefs of Staff, the highest ranking officer in the US military, told Al Jazeera he was not aware of the details of the footage but that the US army was not involved in promoting religion.
"From the United States' military's perspective, it is not our position to push any specific kind of religion," he said at a Pentagon briefing in Washington on Monday.
Under the US military code of conduct, armed forces on active duty are prohibited from trying to convert a person's faith.
Ahmed Shah Ahmedzai told Al Jazeera from Kabul on Monday: "This is a complete deviation from what they [the US military] are supposed to be doing.
"I don't think even the US constitution would allow what they are doing ... it is completely against all regulations.
"This is very damaging for diplomatic relations between the two counties ... everyone knows people are very conservative here, very faithful to Islam. They will never accept any other religion.
"Someone who leaves Islam is sentenced very severely - the death penalty [is imposed].
"There must be a serious investigation now that it has come out into the public and [into the] press," he said.
Sayed Aalam Uddin Asser, of the Islamic Front for Peace and Understanding in Kabul, told Al Jazeera: "It's a national security issue ... our constitution says nothing can take place in Afghanistan against Islam.
"If people come and propaganda other religions which have no followers in Afghanistan [then] it creates problems for the people, for peace, for stability.
Local language bibles
The footage, shot about a year ago by Brian Hughes, a documentary maker and former member of the US military who spent several days in Bagram near Kabul, was obtained by Al Jazeera's James Bays, who has covered Afghanistan extensively.
In other footage captured at Bagram, Sergeant Jon Watt, a soldier set to become a military chaplain, said during a Bible study class: "I also want to praise God because my church collected some money to get bibles for Afghanistan. They came and sent the money out."
It is not clear that the Bibles were distributed to Afghans, but Hughes said that none of the people he recorded in a series of sermons and Bible study classes appeared to able to speak Pashto or Dari.
Hughes said: "The only reason they would have these documents there was to distribute them to the Afghan people and I knew it was wrong, and I knew that filming it … documenting it would be important."
It is not clear if the presence of the bibles and practice of calling on soldiers to be "witnesses" for Jesus continues, but they were filmed a year ago despite regulations by the US military's Central Command that expressly forbid "proselytising of any religion, faith or practice".
|It is not clear any of the local language Bibles were distributed to Afghans
But in another piece of footage, the chaplains appear to understand their actions were in breach of a regulation known as General Order Number One.
"Do we know what it means to proselytise?" Captain Emmit Furner, a military chaplain, says to the gathering.
"It is General Order Number One," an unidentified soldier replies.
But Watt says "you can't proselytise, but you can give gifts".
The footage also suggests US soldiers gave out bibles in Iraq.
In an address at Bagram, Watt is recorded as saying: "I bought a carpet and then I gave the guy a Bible after I conducted my business.
"... the expressions that I got from the people in Iraq [were] just phenomenal, they were hungry for the word."
Questioned about the footage, Greg Julian, a US colonel in Afghanistan, told Al Jazeera: "Most of this is taken out of context ... this is irresponsible and inappropriate journalism.
"This footage was taken a year ago ... the bibles were taken into custody and not distributed.
"There is no effort to go out and proselytise to Afghans."
The footage has surfaced as Barack Obama, the US president, prepares to host Hamid Karzai, Afghanistan's president, at a summit on Tuesday and Wednesday focusing on how to tackle al-Qaeda and Taliban attacks along the Pakistan-Afghanistan border.