President Trump is not planning to attend a ceremony in Manhattan for the 25th anniversary of the terrorist attack on the World Trade Center, in part because he wanted to deliver a speech and the annual event has long barred remarks, according to four people with knowledge of the events.

Mr. Trump’s team had conducted advance visits at the site and had initially signaled to officials in New York and in Washington that the president intended to visit the memorial space known as ground zero, two of the people with knowledge of the events said.

The president’s interest in speaking on Sept. 11 was conveyed to memorial planners in recent weeks, three of the people with knowledge of the events said. But since 2012, politicians have been barred from speaking at the site. The National September 11 Memorial and Museum, which oversees the site, has worked rigorously to keep the venue nonpartisan and focused on the solemnity of the day.

Mr. Trump, a native New Yorker who talked often about the Sept. 11 attacks during his 2016 presidential campaign, is now expected to commemorate them at the Pentagon, two of the people with knowledge of the events said. The Pentagon also came under attack on Sept. 11, 2001.

Vice President JD Vance is expected to represent the White House in New York.

The president will go to the Pentagon after he attends a midterm political convention in Texas. Officials have discussed some kind of tribute to the terrorist attack victims during that convention, which takes place Sept. 9 and 10.

There are other considerations that led to Mr. Trump honoring the day in Washington, including that he will depart the next day for his golf course in Doonbeg, Ireland, where the Irish Open tournament will take place. Leaving from John F. Kennedy International Airport in New York City, or from Newark Liberty International Airport in New Jersey, would snarl air and motor traffic to a much greater extent than with Mr. Trump leaving from Joint Base Andrews in Maryland.

Mr. Trump last attended the ceremony at ground zero in 2024, when he stood alongside Mr. Vance, former Mayor Michael R. Bloomberg, President Joseph R. Biden Jr. and Vice President Kamala Harris.

None of the officials made formal remarks. Mr. Trump visited a fire station in New York City after the event.

This year’s anniversary marks a quarter-century since the worst attack on the United States after the assault on Pearl Harbor. Anna Kelly, a spokeswoman for the White House, did not address the president’s plans in a response to an email seeking comment.

“On the 25th anniversary of this tragic day, the president will remember those who were killed at the hands of evil terrorists, honor their loved ones, and pay tribute to the brave first responders who put their lives on the line to rescue their fellow Americans,” she said.

At the Pentagon, Mr. Trump will be allowed to speak, as he did last year, when he attended the remembrances there. His speech that day came less than 24 hours after the conservative activist Charlie Kirk, whose efforts to draw college-aged voters into the MAGA movement were seen as significant to Mr. Trump’s 2024 victory, was shot and killed while speaking on a campus in Utah.

The ceremony had been intended to be held in a different spot that day, but was moved to a new one amid security concerns about the president after Mr. Kirk was assassinated.

“We recall the light of America’s best and bravest and the love that they showed in their final moments,” Mr. Trump said at the time. “In their memory, we make a solemn pledge and a noble promise. We will honor always our great heroes, and you are our heroes.”

The president has faced two assassination attempts and other murder-for-hire plots by alleged Iranian proxies. He has faced an uptick in threats since he began a war against Iran on Feb. 28.

This year’s event in Manhattan is expected to include former Mayor Rudolph W. Giuliani; former President Bill Clinton and his wife, Hillary Clinton; former President George W. Bush and his wife, Laura; and former President Barack Obama, among others, according to several people who have been close to the planning.

In the first decade after Sept. 11, elected officials would read poems and historic American documents, like the Gettysburg Address, at the ceremony. But since 2012, the memorial has barred any speeches by politicians. Instead, politicians stand alongside their peers from opposing parties as families step onto a stage to read the names of the dead over the course of hours.

Mr. Trump’s advisers have discussed possibly taking federal control of the National September 11 Memorial and Museum, including as recently as last year. Families of the Sept. 11 victims have in recent years criticized the site over its leadership and finances.

Mr. Trump, who was in New York on the day of the attacks, spoke to a New Jersey television station in the aftermath, saying that a building he owned had gained in stature because the twin towers had fallen. That building, 40 Wall Street, “actually was the second-tallest building in downtown Manhattan, and it was actually — before the World Trade Center — was the tallest.”

He went on, “And then, when they built the World Trade Center, it became known as the second-tallest. And now it’s the tallest.” (The statement was not correct; 70 Pine Street, nearby, was taller than Mr. Trump’s building.)