Mayor Eric Adams on Tuesday demanded that the federal government stop making arrests at New York City immigration courts, marking a break with President Trump’s crackdown on illegal immigration as the mayor runs a long-shot re-election campaign.

Mr. Adams, along with the city’s top lawyer, Muriel Goode-Trufant, said that New York City had filed a brief in support of a lawsuit challenging the administration’s authority to detain people who show up for mandatory immigration hearings.

The brief claims that New York City’s leaders “cannot effectively govern” if many residents are too frightened to appear for routine legal proceedings. The detention practice, the city argues, threatens to “deter people from accessing the court system on which local governance depends.”

“We should allow New Yorkers to feel secure to attend legal proceedings in their pursuit to obtain legal status,” Mr. Adams said in a statement, adding that “no one in our city should feel forced to hide in the shadows.”

Mr. Adams was indicted on federal corruption charges last fall and for months drew closer to President Trump as he lobbied the government to abandon the case. The mayor publicly supported some of the president’s policies targeting migrants, and the charges against him were ultimately dropped after prosecutors said they were hindering him from helping with the administration’s deportation campaign.

The mayor’s statement on Tuesday showed that alliance under strain as Mr. Adams tries to win a second term and distances himself from the president, who is widely unpopular in New York City.