The US Justice Department on Monday ordered federal prosecutors to drop corruption charges against Democratic New York Mayor Eric Adams, US media reported, after his rapprochement with President Donald Trump.

"You are directed, as authorised by the Attorney General, to dismiss the pending charges in United States v Adams," said the department memo obtained by the New York Times and CNN.

The first sitting New York mayor to be criminally indicted, Adams in September pleaded not guilty to charges of fraud and bribery, and rebuffed calls for his resignation.

The shocking corruption scandal bode ill for his reelection bid in the November mayoral race.

Adams has also asserted, without evidence, that he was being punished for his criticism of former President Joe Biden's immigration policies.

And Trump, who himself was facing multiple legal troubles, expressed solidarity with Adams during his election campaign, saying the mayor was being prosecuted "for speaking out against open borders".

Adams' lawyer Alex Spiro praised the move in an email statement to AFP.

"As I said from the outset, the mayor is innocent - and he would prevail. Today he has," Spiro said.

"Despite a lot of fanfare and sensational claims, ultimately there was no evidence presented that he broke any laws, ever," he added.

"Now, thankfully, the mayor and New York can put this unfortunate and misguided prosecution behind them."

A man once touted as a future Democratic Party star, Adams has ramped up contact with associates of Republican US President Donald Trump in recent weeks.

In December, he met with border czar Thomas Homan - charged by Trump with plans to deport undocumented immigrants - and some on the left suspect the mayor of seeking a presidential pardon in exchange for rapprochement with the administration.

Emil Bove, the Justice Department's acting deputy attorney general and a former lawyer for Trump, in the letter accused the former Manhattan federal prosecutor of pursuing Adams for his own political gains.

He said the investigation was conducted too close to the Democratic primaries for the upcoming New York mayoral election in November.

According to the New York Times, Bove also argued that the indictment had hindered Adams' ability to cooperate with the Trump administration in its crackdown on immigration.

Adams has been accused of wire fraud, soliciting illegal campaign donations and a bribery conspiracy involving Turkish citizens and at least one Turkish official.

According to the charges, he accepted luxury international flights, hotel suites and free high-end restaurant meals including from Turkish associates in return for favours.

In one example, prosecutors say Adams pressured the city's fire department to approve Turkey's new high-rise consulate in Manhattan despite safety concerns.

AFP