President Obama today mourned the four Americans killed in this week's attack on the U.S. Embassy in Libya as their remains arrived on U.S. soil, remembering them as patriots who embodied the America ideal and declaring that the United States will never "stop working for the dignity and freedom that every person deserves."

Addressing the families of Ambassador Chris Stevens, Sean Smith, Glen Doherty and Tyrone Woods as he stood alongside their flag-covered cases, the president vowed "their sacrifice will never be forgotten."

Obama recalled each man personally in the somber ceremony at Andrews Air Force Base near Camp Springs, Md. "Four Americans, four patriots," he said. "They loved this country, and they chose to serve it and served it well. They had a mission and they believed in it. They knew the danger and they accepted it.

"They didn't simply embrace the American ideal, they lived it, they embodied it. The courage, the hope and, yes, the idealism, that fundamental American belief that we can lead this world a little better than before. That's who they were and that's who we are. If we want to truly honor their memory, that's who we must always be," he said.

The president vowed to bring justice to their killers and underscored the importance of remembering the message the victims sent to the world: "that America is a friend."

"The United States of America will never retreat from the world," he said. "We will never stop working for the dignity and freedom that every person deserves, whatever their creed, whatever their faith. That's the essence of American leadership. That's the spirit that sets us apart from other nations. This was their work in Benghazi, and this is the work we will carry on."

The attack on the consulate in Benghazi comes amid an outbreak of violence at U.S. embassies in Muslim countries linked to an online anti-Islam film. U.S. officials are investigating whether the deadly assault in Libya was a pre-planned attack intended to coincide with the 9/11 anniversary or tied to the broader protests in the region.

Vice President Joe Biden, Secretary of State Hillary Clinton, and Defense Secretary Leon Panetta were also in attendance at today's transfer ceremony.