US President Donald Trump has hailed himself a “king” as he used his powers to bring an end to congestion pricing in New York.

The federally approved program had been intended to reduce traffic and raise money to upgrade New York City’s ageing subway and bus systems.

On Wednesday (US time), Trump declared the city “saved” after his administration announced it would rescind the plan’s Biden-era approval.

“CONGESTION PRICING IS DEAD. Manhattan, and all of New York, is SAVED,” he posted on Truth Social. “LONG LIVE THE KING!”

On X, the official White House account repeated the post and accompanied it photo of a smiling Trump wearing a crown.

It came after protesters turned out in many US cities on Monday, including New York, dubbing the Presidents Day holiday as “No Kings Day”.

Under the program, which launched on January 5, most passenger vehicles are charged $US9 ($A14) during peak periods to enter Manhattan south of 60th Street.

Trucks and buses pay up to $US21.60. The fee is reduced by 75 per cent at night.

US Transportation Secretary Sean Duffy said cancelling it would halt a program that “leaves drivers without any free highway alternative, and instead, takes more money from working people to pay for a transit system and not highways”.

The Metropolitan Transportation Authority and a New York bridge authority quickly filed suit in Manhattan seeking to block the move.

They said the decision was made “for blatantly political reasons” – to uphold a Trump campaign promise.

New York Governor Kathy Hochul has said that money raised by the program would underpin $US15 billion in debt financing for mass transit capital improvements.

On Wednesday, she said the program had been a huge success, reducing commuting times and helping kids on school buses get to classes on time.

“We are a nation of laws, not ruled by a king,” she said. “We’ll see you in court.”

Congestion pricing, which New York City had estimated would bring in $US500 million in its first year, was approved in the final months of former president Joe Biden’s administration.

Because it involved tolls on federal highways, it required US approval.

Transit officials say the program has cut commuting times and that inbound trip times on all Hudson River and East River crossings are now 10 per cent to 30 per cent faster or more, while bus services had also improved.

Subway ridership had grown since the toll was introduced.

Before the fee, New York said more than 700,000 vehicles entered central Manhattan daily, slowing traffic to 11km/h on average, which is 23 per cent slower than in 2010.

-with AAP