New York, New York - Governor Kathy Hochul fired back after President Donald Trump's administration moved to kill New York's nascent congestion pricing scheme designed to ease traffic and finance public transport by imposing tolls on drivers in Manhattan.

The $9 daytime toll for motorists entering areas of Manhattan south of Central Park was introduced in early January after being approved at the last minute before the inauguration of the Republican president – a native New Yorker.

In a letter to New York Governor Kathy Hochul, Transportation Secretary Sean Duffy terminated approval for the pilot program, sparking an immediate backlash from city officials.

But Trump celebrated the move on his Truth Social network, posting: "CONGESTION PRICING IS DEAD. Manhattan, and all of New York, is SAVED. LONG LIVE THE KING!"

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Hochul hit back, posting on X her support of the program, saying it was proving a success and gaining backers "every day".

"We are a nation of laws, not ruled by a king," she wrote. "We'll see you in court."

In a press conference, she said the move was "an attack on our sovereignty and independence from Washington."

The city's Metropolitan Transportation Authority quickly filed a lawsuit to challenge the order.

"The MTA filed papers in federal court to ensure that the highly successful program – which has already dramatically reduced congestion, bringing reduced traffic and faster travel times, while increasing speeds for buses and emergency vehicles – will continue notwithstanding this baseless effort to snatch those benefits away," CEO Janno Lieber said in a statement.

At the time the toll went into effect, some 700,000 vehicles entered the congestion zone every day, and gridlock meant cars could travel just seven miles per hour on average, according to officials.

The congestion pricing plan also aimed to combat air pollution.

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Environmental non-governmental group Evergreen Action criticized the Trump administration's action as a "reckless, illegal move to dismantle critical climate and economic policies."

Similar driver-tolling schemes have been operated for years in other megacities, including London and Stockholm, but opposition and legal challenges ahead of implementation in New York highlighted the difficulty of charging drivers in a country where the car is king.