Allied forces secured the beaches at a cost of about 10,000 casualties in what was the first step in a campaign that would, in a matter of weeks, liberate Paris, which had been under Nazi occupation for more than four years.

President Obama joined Britain's Prime Minister Gordon Brown, France's President Nicolas Sarkozy and Canada's Prime Minister Stephen Harper at a ceremony at the American Cemetary in Normandy, close to where many died in the World War II offensive.

Brown praised those who fought on that day, saying, "as long as freedom lives, their deeds will never die."

He said their sacrifices had put obligations on people living today in what he called "the great covenant of D-Day.

"We must be as if liberators for our day and our generation too," he said, citing Burma (renamed Myanmar) and Zimbabwe, as well as the "mortal threat of poverty, hunger, illiteracy, disease and want."

We will never forget all of those who gave their lives so we can have freedom in ours.