NEW YORK — Mayor Bill de Blasio’s duties and dreams have, at times, been at odds.

For example, de Blasio on Wednesday canceled a campaign-style trip to New Hampshire — part of a wink-wink flirtation with a potential presidential run — after the tragic “friendly-fire” death of police detective Brian Simonsen.

Simonsen was killed Tuesday night after he and other officers confronted a robbery suspect in a cellphone store in Queens. The detective, wearing civilian clothing, was mortally wounded during a barrage of fire from other officers as he exited the store, according to the police.

The detective’s death led de Blasio to call off a trip to New Hampshire that he had planned for Friday, where he was to meet with the mayor of Nashua, Jim Donchess, and local activists in Concord. The trip was first reported by Politico, which also reported that the mayor’s schedule might also include chatting with Nashua residents at a diner.

In 2017, de Blasio was fiercely criticized when he flew to Germany a day after a police officer, Miosotis Familia, was shot to death while on duty in the Bronx. On that trip, de Blasio gave a speech at a protest rally in Hamburg, where President Donald Trump, President Vladimir Putin of Russia and other world leaders were meeting at a Group of 20 summit. De Blasio returned in time to attend Familia’s funeral.

At a news conference at a Brooklyn school Wednesday, de Blasio was asked to explain why he canceled the New Hampshire trip and whether the criticism he received following Familia’s death was a factor.

“Every situation is individual, obviously, but I just felt, for something that was not governmental, that it wasn’t appropriate at this point in time,” de Blasio said. “Just as simple as that.”

De Blasio has been criticized for seeking to build a national profile and project himself as a leader of progressive Democrats beyond the city he governs. And he seems unaffected by recent polls and incredulous media coverage that have underscored the improbability of his presidential ambitions.

“I have my whole life dreamed of making a difference,” the mayor said Wednesday. “I have felt my whole life that I have had a mission and a sense of calling. I didn’t know what form it would take but I do know this is what I’m going to devote my life to, to trying to make this a more just society.”

The New Hampshire trip was to be paid for by a federal political action committee that de Blasio formed last year, called Fairness PAC. In recent weeks he has played coy by not ruling out the possibility of running for president in 2020.

He has also said that he plans to go around the country “preaching the gospel” of the liberal policies he has enacted in New York, such as expanded early childhood education — a theme he revisited Wednesday.

The news conference Wednesday started with the mayor urging parents to participate in elected education councils that provide input on school policy. He then fielded questions about education-related issues and the death of Simonsen. But the questions kept coming back to his unlikely presidential aspirations and the conflict between duties and dreams.

Wouldn’t the demands of his job as mayor make it difficult to conduct a national campaign?

“Would you rather have as president of the United States someone who had had a less demanding job?” de Blasio said. “And I’m someone saying I’m going out around the country to raise issues so I’m not talking about myself, I’m talking about the general point for a job of that magnitude, wouldn’t you want someone who had served in an executive function in the most trying circumstances?”

City Hall officials said that de Blasio still planned to travel to Boston on Thursday for an event at the Harvard Kennedy School in his capacity as mayor.

The mayor did not say if or when he would reschedule his trip to New Hampshire.

This article originally appeared in The New York Times.