Today marks the 17th anniversary of September 11th, a day when almost 3,000 people died and 6,000 were injured following a terror attack on the World Trade Center.
Paying tribute to the victims, he said: "Seventeen years ago, 40 incredible men and women show the whole world no force on Earth will ever conquer the American spirit".
"A piece of America's heart is buried in this field", Trump said.
He said: "This field now now a message to the world: America will never submit to tyranny".
As the world remembers the thousands of people who lost their lives in the attack on the World Trade Center, President Trump flew to Johnstown, Pennsylvania with Melania this morning to attend a memorial event.
The names are read by victims' loved ones, some of them not yet born when the attacks happened.
Felt, whose brother Edward died aboard Flight 93, recalled that the passengers came together and developed a plan to confront the terrorists "in just 35 minutes", having learned that hijacked planes had already been flown into the two towers of the World Trade Center and the Pentagon.More news: Grading the Bears: Tough night for many vs. Packers QB Aaron Rodgers
Bin Laden was killed nearly a decade later, in May 2011, during a military operation ordered by President Barack Obama.
Trump observed the anniversary for the first time as president past year, along with the first lady, at the White House.
"As long as this monument stands, as long as this memorial endures, fearless patriots will rise up in America's moments of need, and they too will fight back".
While on his way to the memorial service, the president tweeted: "17 years since September 11th!". He also tweeted quotes from Fox News about a series of familiar grievances, including the Russian Federation probe and the Department of Justice. Trump, a Republican and native New Yorker, took the occasion of last years anniversary to issue a stern warning to extremists that "America can not be intimidated".
"17 years since September 11!" he wrote.
At the Pentagon, where 184 people died when American Airlines Flight 77 struck the building, Vice President Pence said, "A growing number of Americans have no living memory of what happened here". He has a mixed history with September 11, often using the terrorist strikes to praise the response of New Yorkers to the attack but also making unsubstantiated claims about what he did and saw that day.
Memorials to 9/11 continue to grow at Shanksville, where a newly dedicated Tower of Voices will eventually include a wind chime for each of the 40 people killed there, and ground zero, where work is to begin soon on a pathway honoring rescue and recovery workers.