Gates' remarks come amid reports of U.S. forces killing civilians on a bus near Kandahar in Afghanistan. The video from Iraq was taken in 2007 by Army Apache helicopters when troops mistook a camera for an AK-47 and a long-range lens as a rocket-propelled grenade launcher. The video was released online by Wikileaks.org.
The video, released by Wikileaks.org, shows the group of men walking down the street before being repeatedly shot by the helicopters. The gunners can be heard laughing and referring to the men as "dead bastards."
"People can put out anything they want and not be held accountable. There's no before and no after, just the present," Gates said of the video.
The result is that "you're looking at a situation through a soda straw and you have no context or perspective," he added.
A military investigation found that the troops acted appropriately. U.S. officials say the Reuters employees were in the same vicinity as armed men walking toward a firefight, where ground troops had requested air support.
Gates also defended U.S. rules of engagement in Afghanistan, saying that that the military takes extreme caution in avoiding civilian casualties but some deaths are unavoidable.
"Let's also face the reality that we are in a war and our adversaries ... use civilians. They purposely put civilians in harm's way," Gates said.
Gates spoke to reporters en route to South America, where he planned to meet with leaders from Peru and Colombia countries whose militaries have been accused of human rights abuses in the past, but whose cooperation on matters like counternarcotics have been crucial to U.S. interests.
Gates' trip is seen as an effort to shore up U.S. support in a region where Iran is trying to expand its influence, and where Russia and China are making commercial inroads.
When asked whether recent incidents of civilian casualties in Iraq and Afghanistan have undercut the U.S. position on human rights, Gates said no.
"In Afghanistan, I don't recall a single (incident) where someone alleges the United States did it on purpose," he said. "Where there have been civilian casualties, they were tragic incidents" where civilians were caught in the crossfire.
Gates also defended Gen. Stanley McChrystal, the top U.S. and NATO commander in Afghanistan, saying McChrystal is very concerned about protecting civilians.
"Every time I talk to Gen. McChrystal, he talks about this. His view is the civilian casualty question is a strategic question in Afghanistan" and it's why "he's been as aggressive as he has."
Gates' remarks come amid reports of U.S. forces killing civilians on a bus near Kandahar in Afghanistan.
Gates' trip to South America comes on the heels of a new defense cooperation agreement with Brazil. Gates said the U.S. could expand cooperation with Peru and Colombia in military training. He also said Peru has been a "constructive influence" in South America in trying to "counter some of the propaganda" from Venezuela.
"They have their own interests, but the reality is they've been a good friend to the United States," he said.
The video is posted below as it appears on Wikileaks.org. It is graphic in nature: