Tension among Mayor Bill de Blasio, the MTA, and the subway workers' union spiked further Sunday during the opening of the first city-funded subway station in more than 60 years.

At the opening ceremony for the $2.4 billion station, the head of the state-run MTA pushed the mayor on the deficit in the $26.8 billion capital plan, which funds big projects like the Second Avenue Subway.

"Mayor de Blasio, we appreciate your support of this project, but we need your help," MTA chairman Thomas Prendergast said.

"Without the $3.2 billion that we need from the city, we will be unable to meet the capital needs that we need desperately for the program."

De Blasio then said the city and its residents pay for much of the MTA already -- and that the federal government needs to pony up more transportation funding.

"I think it's very important we remember the facts. The City of New York and the people of New York are the backbone of the funding of so much of the MTA," he said.

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"We pay 73 percent of the MTA's budget through the city government's contribution, through the fares our people pay, the tolls our people pay, the taxes our people pay. We are doing our share."

MTA spokesman Adam Lisberg took shots at de Blasio's reckoning on the city's support.

"His math is wrong," Lisberg said. It's a way of saying that the city shouldn't contribute its own money to the MTA because people who live in the city pay fares to ride the subway. It's fuzzy math, and like anything else fuzzy, it obscures the real picture."