NEW YORK — A significant business partner of Michael Cohen, President Donald Trump’s personal lawyer, has agreed to cooperate with the government as a potential witness, a development that could be used as leverage to pressure Cohen to work with the special counsel examining Russian interference in the 2016 presidential election.

Under the deal reached with the New York attorney general’s office, the partner, Evgeny A. Freidman, a Russian immigrant who is known as the Taxi King, specifically agreed to assist government prosecutors in state or federal investigations, according to a person briefed on the matter.

The broadened scope of Freidman’s cooperation may prove worrisome not only to Cohen, who is the target of an ongoing federal investigation, but also Trump.

The president’s lawyers are already resigned to the strong possibility that the continuing inquiry into Cohen’s businesses could lead him to cooperate with federal prosecutors. That likelihood may now be greater, with Freidman potentially sharing what he knows with federal prosecutors in New York and the special counsel.

Freidman has been Cohen’s partner in the taxi business for years, managing cabs for him even after New York City regulators barred Freidman last year from continuing to manage medallions.

Cohen’s lawyer, Stephen Ryan, declined to comment on Tuesday.

Trump’s lawyers sought to distance their client from the case.

“He’s just not involved in the taxis,” said one of his lawyers, Rudy Giuliani, the former mayor of New York. “He has as much involvement in it as I do.”

Freidman, who was disbarred earlier this month, had been accused of failing to pay more than $5 million in taxes and faced four counts of criminal tax fraud and one of grand larceny — all B felonies. Each carries a maximum prison sentence of up to 25 years in prison.

Instead, he appeared in court in Albany, New York, on Tuesday and pleaded guilty to a single count of evading only $50,000 worth of taxes; he will avoid jail time and receive five years of probation if he fulfills the terms of his agreement, the judge, Patrick Lynch of Albany County court, said during the roughly 20-minute proceeding.

Later Tuesday, Freidman emailed a New York Times reporter about the article that had been published about his guilty plea, calling it “shameful” and comparing it to a tabloid story. “Michael is dear dear personal friend and a passive client! That’s it!” he wrote. “I am humbled and shamed!” he said, adding that the guilty plea represented “me taking responsibility for my actions.”

“I had been an officer of the court in excess of 20 years and now I am a felon!” he wrote. “I hate that I have been grouped in this runaway train that I am not a part of!”

But asked if he was cooperating with the authorities, Freidman would not respond.

After Freidman’s guilty plea, his lawyer, Patrick J. Egan of Fox Rothschild, declined to comment. But earlier this year he said his client “considers Michael a very good friend and a great client.”

Nonetheless, Freidman’s agreement to cooperate in his tax fraud case in Albany could have larger implications. Cohen is facing an investigation by the U.S. attorney’s office in Manhattan, which is examining his business practices. Anything that bolsters that inquiry could increase pressure on Cohen to cooperate with Robert Mueller, the special counsel who is investigating the 2016 election that led to Trump’s victory.

Last month, federal agents carried out search warrants at Cohen’s home, his office and a hotel room where he was staying. The search sought a wide range of materials, including documents related to his business associates and accountants, as well as a $130,000 payment to Stephanie Clifford, the adult film actress known as Stormy Daniels, who has said she had an affair with Trump.

Cohen is best known as Trump’s personal lawyer, a role given more prominence by actor Ben Stiller’s recurring portrayal of him on “Saturday Night Live.” But he has a wide range of business interests of his own that have drawn scrutiny, from taxicabs to real estate to a failed casino boat.

Cohen and an earlier partner in the taxi business managed a company that operated 260 yellow cabs in the early 2000s, a huge fleet that brought in millions of dollars in annual revenue — much of it in cash. Today, he still owns 32 taxi medallions in New York and 22 in Chicago, a portfolio estimated to be worth at least $10 million.

In recent weeks, some prominent corporations have been embarrassed by revelations that they paid Cohen after the election to gain entree to the Trump administration. The top lawyer at Novartis retired over the issue, and AT&T’s head of lobbying and external affairs also departed.

While Cohen performed a relatively small amount of actual legal work for Trump, he carried out a wide range of tasks during his decade at the Trump Organization.

He scouted real estate deals for Trump from Fresno, California, to the Republic of Georgia; served as the chief operating officer of a failed mixed martial arts venture; started a website to drum up interest in a 2012 presidential run that never materialized; and was a point man in responding to allegations of impropriety at Trump University. That wide range of work could make Cohen a valuable witness for federal investigators.

Even before Cohen went to work for Trump in 2007, he began to step back from direct management of the taxi cab business, eventually turning to Freidman to run his cabs.

The charges against Freidman stem from accusations that he pocketed a 50-cent surcharge, known as the Metropolitan Transportation Authority tax, which is used to pay for mass transit improvements. When he was charged last year, Nonie Manion, then the acting commissioner of the state Department of Taxation and Finance, said “this indictment exposes a blatant scheme to shortchange the Metropolitan Transportation Authority, the transportation infrastructure relied on by millions of New Yorkers.”

Freidman would also be required to pay $1 million in restitution to the state attorney general’s office.

“Today, the ‘Taxi King’ admitted that he built his empire by stealing from New Yorkers,” said Barbara Underwood, the state attorney general. “Freidman pocketed money that should have provided much-needed investment in our transit system — and he’ll now have to pay back every cent. Our office will continue to hold accountable those who cheat the system.”

During the court hearing Tuesday, Freidman, dressed in a neat gray jacket and black pants accented with zippers, spoke softly and haltingly. His jury trial had been scheduled for June 18.

Toward the end of the hearing, Lynch asked Freidman if he “understood the nature of the benefit” his attorneys had accomplished on his behalf.

Freidman said he had “spent long hours” speaking with his lawyers, adding, “I’m extremely satisfied with the services that have been provided to me.”