The MTA’s hasty decision to retain 500 new police officers will exacerbate its already dire financial situation, growing its deficit to $1 billion in the coming years, according to a new analysis released Wednesday.

Transit officials announced plans earlier this month to hire the officers as part of Gov. Andrew Cuomo’s multi-pronged strategy to tackle fare evasion and assaults on transit workers and riders.

At the time, the MTA said funding for the new jobs would come from $40 million provided by Manhattan District Attorney Cy Vance.

But the cost of the hiring spree far exceeds Vance’s contribution — to the tune of $260 million over the next four years and nearly $1 billion over the next decade, according to numbers crunched by fiscal watchdog Citizens Budget Commission.

The calculation is based on the cost per additional officer — at least $93,000 per head — plus the cost to employ another 81 supervisors to manage them. The total bill will rise from $56.1 million in the first year to $119.9 million 10 years down the road.

The MTA faces massive operating deficits and has already reduced bus service to make ends meet. Agency officials anticipate a $740 million shortfall over the next four years.

“Adding to [the deficit] should be only done with extreme care and considering the trade-offs,” Citizens Budget Commission President Andrew Rein told The Post. “Ultimately, somebody has to pay the bill — or we need to find [ways to cut costs] within the MTA.”

At Wednesday’s MTA board meeting, city appointee Bob Linn questioned whether the plan to add officers had been fully thought through.

“You’re talking about annual costs of $100 million. Where have we talked about how that’s going to be budgeted?” he said. “What I keep seeing is solutions announced first, and then you see whether the data supports it.”

The MTA has had to face down a number of “quality of life” issues this summer, including upticks in assaults against transit workers, in delays caused by homeless individuals and in several major crime categories.

“Our customers and employees demand security and safety,” MTA Communications Director Tim Minton said in a statement. “We have to deliver on a pact with riders and the people who work so hard to get them where they’re going to make sure everyone arrives safely. We will do it in the cost-effective way possible.”