NEW YORK CITY -- Federal prosecutors said Wednesday they are pursuing "several related investigations" that could lead to additional corruption charges against New York City Mayor Eric Adams and indictments for people in his orbit.

Prosecutors made the disclosure as the first-term Democrat attended a court hearing days after he was indicted on charges that he accepted about US$100,000 worth of free or deeply discounted international flights, hotel stays, meals and entertainment, and obtained illegal campaign contributions from foreign interests.

The allegations span nearly a decade, dating to when Adams was Brooklyn's borough president. U.S. District Judge Dale Ho didn't immediately set a date for his trial, which prosecutors estimated will take about four weeks. Adams's lawyer, Alex Spiro, asked to hold the trial in March, before an important ballot deadline for next June's mayoral election.

Prosecutors say Adams's travel perks were arranged by a senior Turkish diplomatic official in New York and Turkish businesspeople who wanted to gain influence with Adams. The indictment alleges that Adams, a Democrat, also conspired to receive monetary donations to his political campaigns through straw donors from foreign sources who weren't allowed to give money to U.S. political candidates.

Assistant U.S. Attorney Hagan Scotten told Ho that it is "quite likely" prosecutors will seek a superseding indictment and that it is "likely" additional defendants will be charged and "possible" that more charges will be brought against Adams, who pleaded not guilty last week to the current charges against him.

"There are several related investigations here," Scotten told the judge.

Scotten said some of the evidence includes Turkish Airlines records that show Adams either didn't pay for flights or that he paid a few hundreds dollars for an economy class ticket "to create the illusion that he was paying his way" when he was really receiving free upgrades worth several thousand dollars.

Other evidence includes bank, credit card and phone records, campaign finance filings, emails and text messages, Scotten said. Some of the material, including communications between alleged co-conspirators arranging travel and campaign donations, is written in Turkish, he said. Spiro said the defence would work with prosecutors to ensure that they have access to a locked cellphone that investigators obtained from Adams.

The hearing was Adams's first court appearance since his arraignment on Friday.

"Busy. Busy. Busy city. Running the city. Making sure we continue to move forward," Adams said as he stepped out of a black SUV and walked into the courthouse.

He didn't speak after the hearing but gave a quick thumbs up before he stepped back into the vehicle to head to a police briefing on increased security for the Jewish High Holidays.

Inside the courtroom, Adams mostly sat quietly at the defence table with his hands in his lap as the judge set a schedule to deal with complaints that his lawyers have been airing in court filings and media appearances about the charges and investigation. At one point, as his lawyer spoke from a nearby lectern, Adams leaned forward in his seat and scribbled notes on a legal pad.

Adams's lawyers have filed motions seeking to dismiss the bribery charge against him and seeking an inquiry into whether prosecutors improperly leaked information to reporters about the investigation.

The U.S. attorney's office will have until Oct. 18 to respond in writing. The defence will then have until Oct. 25 to file additional paperwork, with arguments scheduled for Nov. 1.

Adams's indictment alleges that he reciprocated gifts he received from the Turkish official and businesspeople in 2021 by helping Turkey open a new diplomatic facility in the city despite concerns that had been raised by the Fire Department about whether the building could pass all of its required fire safety inspections.

Adams has denied knowingly accepting any illegal campaign contributions. He also said there was nothing improper about the trips he took abroad or the perks he received, and that any help he gave to Turkish officials regarding the diplomatic building was just routine "constituent services." He has said helping people navigate the city's bureaucracy was part of his job.

A spokesperson for Turkey's Ministry of Foreign Affairs, Oncu Keceli, said in a statement that the country's missions in the U.S. and elsewhere operate according to international diplomatic rules and that "Our meddling in another country's internal affairs is out of the question."

In seeking to dismiss the bribery charge, Adams's lawyer, Alex Spiro, argued that the mayor's flights, upgrades, meals and hotel rooms do not count as bribes under federal law.

The defence's motion regarding potential leaks didn't cite any evidence that prosecutors broke grand jury rules, but it cited a string of news reports by The New York Times about instances in which the investigation burst into public view, such as when FBI agents searched the home of one of Adams's chief fundraisers and when they stopped the mayor as he left a public event last November and seized his electronic devices.

Adams is likely to face several challengers in next June's Democratic primary. Spiro said he wants to finish the trial before a March deadline for candidates to be certified for that ballot.

"I'm not going to be asking for further delay," Spiro said. Prosecutors did not object, and Ho said he would take Spiro's request "under advisement" and make a decision at a later date.

"The public and Mayor Adams have an interest in a speedy trial here, and I agree that interest is heightened" in light of the election calendar, the judge said.