President Trump paid tribute on Monday to the victims and survivors of 9/11, telling Americans on the 16th anniversary of the terrorist attacks that his administration is committed to doing "whatever we must to keep our people safe."

The president and first lady joined thousands of service members and families of 9/11 victims at the Pentagon, where hundreds of military personnel were killed after a hijacked plane crashed into the western side of the complex on Sept. 11, 2001.

"For the families with us on this anniversary, we know that not a single day goes by when you don't think about the loved ones stolen from your life," Trump said. "Today, our entire nation grieves with you and with every one of those 2,996 innocent souls who were murdered by terrorists 16 years ago."

Trump combined his solemn remarks with a promise to protect Americans from future domestic terror attacks by "making plain to these savage killers that there is no dark corner beyond our reach, no sanctuary beyond our grass and nowhere to hide on this Earth.

"America does not bend," the president told the crowd. "We do not waiver and we will never ever yield. So here at this memorial, with hearts both sad and determined, we honor every hero who keeps us free, and we pledge to fight together, to work together and to overcome together every enemy and obstacle in our path."

A lifelong New Yorker, Trump said the World Trade Center attacks marked an "extraordinary" day in U.S. history — a day when Americans across the country emerged "stronger and more determined than ever" to defend themselves and others against grotesque acts of terror.

"The horror and anguish of that day were seared into our national memory forever," Trump said. "On that day not only did the world change, but we all changed. Our eyes were opened to the depths of the evil we face.

"But in that hour of darkness," he continued, "we also came together with renewed purpose. Our differences never looked so small, our common bonds never felt so strong."

The president and first lady were joined by Defense Secretary Jim Mattis and Joint Chiefs Chairman Gen. Joseph Dunford, both of whom are scheduled to participate in a private ceremony later Monday for relatives of those killed during the 9/11 attack on the Pentagon.

Vice President Mike Pence will also deliver remarks in Shanksville, Pa., where 39 passengers who boarded United Airlines Flight 93 on Sept. 11 were killed after hijackers crashed the plane into a field 150 miles away from Washington.