The Trump administration has instructed New York City to end its congestion pricing program, the first of its kind in the nation, by March 21 in a newly released letter.

The Federal Highway Administration said the Metropolitan Transportation Authority must stop collecting tolls by that date to allow for an “orderly cessation.”

The letter is dated Feb. 20, a day after the U.S. Department of Transportation said it pulled federal approval of the plan following a review requested by President Donald Trump.

New York officials have said they will not turn off the tolls without a court order.

“We have said that you may have asked for orderly cessation, which was the phrase that came in the letter to us. I will propose something in the alternative — orderly resistance,” New York Gov. Kathy Hochul said during remarks before the MTA board on Wednesday.

The MTA said it is challenging the Trump administration’s reversal in federal court, seeking a declaratory judgment that the DOT’s move is not proper.

The congestion pricing plan, which launched on Jan. 5, charges passenger vehicles $9 to access Manhattan below 60th Street during peak hours as part of an effort to ease congestion and raise funds for the city’s public transit system. During peak hours, small trucks and charter buses are charged $14.40 and large trucks and tour buses pay $21.60.

Hochul called the program’s early success “genuine” and “extraordinary” in her remarks to the MTA board.

The toll generated nearly $50 million in revenue in its first month, the MTA said this week.

From Jan. 5 to Jan. 31, tolls from the congestion pricing program generated $48.66 million, with the net revenue for that period $37.5 million when taking into account expenses to run the program, the MTA said.

The program is on track to generate $500 million in net revenue by the end of this year, as initially projected, the MTA said.

Congestion has also “dropped dramatically” since the program went into effect, Hochul said last week.

ABC News’ Clara McMichael contributed to this report.