The singer Justin Timberlake pleaded guilty on Friday to driving while impaired, resolving a case that began with his June arrest on drunken-driving charges in the Hamptons.

As part of his plea, Mr. Timberlake agreed to pay a $500 fine and serve 25 hours of community service for a charity of his choosing. He also agreed to a 90-day suspension of his driver’s license in New York.

The singer, who was originally charged with the more serious crime of driving while intoxicated, entered the plea during an appearance at a 30-seat courthouse in the village of Sag Harbor. He wore a black cardigan and khaki slacks, with a double strand of pearls peeking out from beneath a dark T-shirt.

During the hearing, Mr. Timberlake looked on with his hands folded in front of him. His original plea agreement stipulated that he would make a public safety announcement discouraging drinking and driving. Justice Carl Irace, the village court judge overseeing the case, said on Friday that it would be more meaningful for the singer to commit himself to “a period of reflection and contemplation” through community service.

Mr. Timberlake agreed, and acknowledged that he had erred in driving rather than calling a taxi or getting a ride from a friend.

“It was a clear misjudgment,” he said.

Justice Irace, satisfied with Mr. Timberlake’s contrition, commended him for his sincerity. The judge also asked about drug and alcohol counseling for the singer, calling its absence from the plea deal “concerning,” but did not impose it.

Speaking in front of a throng of reporters and cameras outside Sag Harbor Police Headquarters after the hearing, Mr. Timberlake urged people following the case to learn from his mistake.

“Many of you have probably been covering me for a lot of my life, and as you may know, I try to hold myself to a very high standard, for myself, and this was not that,” he said.

The arrest occurred in the early hours of June 18, when a Sag Harbor police officer pulled over a new-model BMW that was driving erratically.

Mr. Timberlake, glassy-eyed and smelling of alcohol, was at the wheel, according to an arrest report. After stepping out of the car, he struggled to complete several sobriety tests, the report said. He was placed in custody and held overnight.

The singer told the police that he was on his way home after having had “one martini.” His lawyer, Edward Burke Jr., insisted to reporters that his client was not drunk when he was arrested. (Mr. Burke’s statements about the charges outside court prompted Justice Irace to scold him at an August hearing.)

The guilty plea concludes a summer of embarrassment for Mr. Timberlake. His arrest inspired a flood of mocking memes and tabloid attention. And even the court dates he did not attend in person drew crowds of reporters and film crews to Sag Harbor’s downtown, where the municipal building is surrounded by clothing boutiques, upscale galleries and the American Hotel. Mr. Timberlake had been seen there imbibing on the night of his arrest.

The legal woes have not interrupted his Forget Tomorrow world tour. He has continued playing stadium concerts, and even cracked a joke about the charges at a show in Boston in June. Justice Irace, acknowledging the demands of Mr. Timberlake’s tour schedule, made the unusual decision to allow the singer to attend the August hearing via video conference from an undisclosed location in Europe.

Mr. Timberlake is scheduled to perform at the Prudential Center in Newark at the end of September as part of a charity show that will benefit a suicide-prevention nonprofit.

Although social media users had a laugh or two at Mr. Timberlake’s expense, some prominent people with ties to the Hamptons sympathized with his public relations headache. In a recent New Yorker profile, the celebrity chef Ina Garten said she felt bad for “poor Justin Timberlake.”

Asked about Mr. Timberlake’s arrest in June, Billy Joel, a Sag Harbor resident who crashed his car three times on Long Island in the early 2000s, advised a local news reporter to “judge not, lest ye be judged.”

On Friday, Sag Harbor’s lesser-known residents were unsympathetic.

Interviewed on Main Street, Helen Hernandez, an accountant with homes in Sag Harbor and Westchester County, said she thought prosecutors should not have agreed to let Mr. Timberlake plead guilty to a less severe charge. Ms. Hernandez said a member of her family had spent $10,000 in legal fees to fight a similar charge in Westchester.

“I’m not a big fan of his,” she said.

Lawrence Rich, a real estate broker who splits his time between Sag Harbor and New York City, said he thought Mr. Timberlake’s celebrity status might have helped his case.

“Rich and famous people get away with things,” he said. “Somebody who’s not rich and famous would be in jail.”

Former President Donald J. Trump sought to move his Manhattan criminal case into federal court on Thursday, filing the unusual request three months after he was convicted in state court.

The long-shot bid marks Mr. Trump’s latest effort to stave off his sentencing in state court in his hush-money trial, in which he was convicted of falsifying records to cover up a sex scandal.

He is scheduled to receive his punishment on Sept. 18, just seven weeks before Election Day, when he will square off against Vice President Kamala Harris for the presidency.

“The ongoing proceedings will continue to cause direct and irreparable harm to President Trump — the leading candidate in the 2024 presidential election — and voters located far beyond Manhattan,” Mr. Trump’s lawyers, Todd Blanche and Emil Bove, wrote in the filing.

Their filing came even as the Trump legal team is awaiting the result of a separate effort to postpone the sentencing; it opened a second front that could complicate the first.

On Aug. 15, Mr. Trump asked the state court judge who presided over the trial, Juan M. Merchan, to delay the sentencing until after Election Day. Mr. Trump’s lawyers argued that they needed more time to challenge his conviction on the basis of a recent Supreme Court ruling granting presidents broad immunity for official acts.

The Manhattan district attorney’s office, which won the conviction of Mr. Trump on May 30, has argued that the Supreme Court’s ruling has “no bearing” on their case, which centers on Mr. Trump’s cover- up of a sex scandal involving a porn star. But the Manhattan prosecutors deferred to the judge on whether to delay the sentencing, leaving the door open for Justice Merchan to punt until after the election.

Justice Merchan was expected to rule on the delay request next week, and it is unclear whether Mr. Trump’s federal petition would disrupt that. In the federal filing, the former president’s lawyers asked a judge to find that Justice Merchan was barred by law from sentencing Mr. Trump while their attempt to move the case was underway.

It seemed possible that effort might backfire. If the federal judge does not grant the lawyers’ request, they will have further alienated Justice Merchan as he prepares to sentence their client. Mr. Trump faces up to four years in prison, though he could receive a shorter sentence, or merely probation.

There are signs the federal judge might be skeptical. Mr. Trump already tried — and failed — to move the case to federal court. Last year, soon after the former president was indicted, he asked the same federal judge to remove the case from Justice Merchan, arguing that it concerned official acts as president.

The judge, Alvin K. Hellerstein, rejected that argument.

“The evidence overwhelmingly suggests that the matter was a purely personal item of the president — a cover-up of an embarrassing event,” Judge Hellerstein wrote in an opinion last year. “Hush money paid to an adult film star is not related to a president’s official acts. It does not reflect in any way the color of the president’s official duties.”

It is unclear how soon Judge Hellerstein might take up Thursday’s request, or whether he will hold a hearing to entertain it. In their filing, Mr. Trump’s lawyers cast aspersions on the New York State court system, saying its procedures had “proven inadequate” to protect federal interests and, if allowed to continue, would “result in further irreparable harm to President Trump.”

The unorthodox filing suggested that Mr. Trump’s lawyers are likely to make any and every attempt they can to delay the sentencing, even if Judge Hellerstein balks.

A spokeswoman for the district attorney’s office declined to comment.

The filing on Thursday captured two of Mr. Trump’s favorite legal strategies: delay, and attacks on Justice Merchan.

The former president has on three occasions sought to oust Justice Merchan from the case, claiming he is biased, and lobbing personal attacks at the judge’s daughter, who is a Democratic political consultant. The judge has rejected each request and assailed the claims as “rife with inaccuracies and unsubstantiated claims.”