President Trump said Monday that terrorists have “nowhere to hide” as he marked the 16th anniversary of the Sept. 11 terrorist attacks in New York, Washington and Pennsylvania.

“These are horrible, horrible enemies — enemies like we've never seen before,” Trump said during remarks at the Pentagon.

“But we're ensuring they never again have a safe haven to launch attacks against our country,” he said. “We are making plain to these savage killers that there is no dark corner beyond our reach, no sanctuary beyond our grasp, and nowhere to hide anywhere on this very large Earth.”

In his first commemoration of the attacks as president, Trump did not use the campaign trail catchphrase “radical Islamic terrorism,” which military leaders, among others, have discouraged as unhelpful.

“The horror and anguish of that dark day were seared into our national memory forever,” Trump said. “It was the worst attack on our country since Pearl Harbor and even worse because this was an attack on civilians — innocent men, women and children whose lives were taken so needlessly.”

Trump also did not mention his proposed temporary ban on immigration from several Muslim-majority nations, which he has said is needed to keep the United States safe from terrorism.

“On that day, not only did the world change, but we all changed,” Trump said. “Our eyes were opened to the depths of the evil we face. But in that hour of darkness, we also came together with renewed purpose. Our differences never looked so small, our common bonds never felt so strong.”

Joint Chiefs of Staff Chairman Gen. Joseph F. Dunford Jr. and Defense Secretary Jim Mattis stood beside Trump as he spoke to a crowd that included families of some of the 184 Pentagon employees and airline passengers and crew who died in the attack there.

“Mr. President, your military does not scare,” Mattis told Trump.

Earlier, Trump led a moment of silence in a brief, somber ceremony at the White House. Trump and first lady Melania Trump walked onto the South Lawn and stood as bells tolled for the first 9/11 anniversary of Trump's presidency. They then bowed their heads and stood silently before placing their hands on their hearts as a bugler played taps.

President Trump and first lady Melania Trump lead a moment of silence at the White House on Sept. 11, to commemorate those who lost their lives on 9/11. (The Washington Post)

Vice President Pence traveled to Shanksville, Pa., where one of the four hijacked jetliners crashed after passengers overpowered the hijackers. He spoke near the rural site of the Pennsylvania crash.

Two planes hit and destroyed the World Trade Center in New York and the other crashed into the Pentagon.

Nearly 3,000 people were killed in the coordinated attacks directed by al-Qaeda leader Osama bin Laden.

Trump, a frequent early-morning tweeter, did not post any messages ahead of the 8:46 a.m. ceremony at the White House.

His New York-based presidential reelection committee issued a statement noting that Trump, a New Yorker, “and many of us in the campaign headquarters in New York City still remember 9-11 as if it just happened.”

“We also join the President in drawing from the memories of this day to inspire and motivate us to ensure that a 9-11 never occurs on our soil again and to confront the evils that persist to destroy our freedoms,” the statement said.