Arena going up — but will the rest of the project?

Atlantic Yards developer Bruce Ratner will not build the $4-billion mega-project unless the economy — and more specifically, the housing market — bounces back.

The developer admitted on Tuesday that all but one of the project’s proposed 16 towers can’t move forward because they are “market dependent.”

“If the [housing] market never comes back, we’re all in trouble,” the developer told reporters after unveiling new designs for the public plaza in front of his Barclays Center arena, a $900-million sports complex under construction near the corner of Atlantic and Flatbush avenues.

That arena, plus one mixed-rent 400-unit tower on the south side of the complex, are insulated from the market conditions that affect the rest of the project — the arena because Ratner has put together the money to build it, and the residential building because it is already being prepped to begin construction early next summer.

Though even that timetable is a few months delayed from a promise made earlier this year by Forest City Ratner executive Jane Marshall.

Ratner’s less-than-rock-solid timeline for the full project contradicted his company’s own press release, which promises “construction of a new residential building beginning every six to nine months” after the start of that first residential tower.

Nonetheless, Ratner said he remains bullish on development in New York and in Brooklyn specifically.

“If there’s no market for the kind of middle-income housing with the amenities and the numbers that we’re doing, then New York City is in serious trouble — but I really don’t think that’s going to happen.”

He declined to speculate when the market for office space will improve, allowing him to move ahead with the project’s design centerpiece, the 50-odd story capstone tower at the Flatbush and Atlantic intersection itself.

“The office market is not good now,” he said. “It could bounce back in a couple of years or many.”

Virtually all of the economic and public benefits of the mega-development — which include more than 2,200 units of below-market-rate housing, thousands of construction jobs, tax revenues for the city, and public space — are dependent on Ratner finishing the project.