The decision to ban such images dates back to 1991 and was taken under George Bush senior, a former US president, during the first Gulf war.
George Bush, his son and also a former president, renewed the ban and was accused of trying to hide the human cost of the wars his administration initiated in Iraq and Afghanistan, which have claimed the lives of nearly 5,000 American soldiers.
Gates said he had ordered a review under the Bush's administration over a year ago but said he reluctantly kept the policy on the advice of his deputies.
"I must say I was never comfortable with it. When I heard the president [Barack Obama] express his concern and desire to have it reviewed, I started the process the next morning," he said.
Gates said there "still is a division" in the Pentagon over the policy.
A CNN and Opinion Research Corporation poll, released on Thursday, showed that a majority of Americans backed the decision to lift the ban, with 67 per cent saying the public should be allowed to see video and photos of the coffins returning.