New York City is poised to pay $2 billion to build a platform over a Manhattan rail yard at the behest of one of the country’s biggest developers, who would then erect mostly luxury housing along the Hudson River.

The tentative deal comes on top of billions in government aid that had already benefited the firm, Related Companies, when it built the first phase of Hudson Yards, a sprawling project that now commands some of the country’s highest apartment rents and steepest office prices.

Related pledged more than 15 years ago to fill the rest of Hudson Yards with residential towers, parks and a public school on Manhattan’s Far West Side. But this second phase of the project never broke ground, with Related claiming that the cost of building over the rail yard had become too high, and that only a more lucrative project, anchored by a casino, would make financial sense.

When community opposition killed Related’s casino bid last spring, the new assistance package quickly rose from the casino bid’s ashes. It was approved in weeks, with Mayor Eric Adams and the City Council agreeing with the developer’s assurances that the complex arrangement made economic sense.

A spokesman for the City Council said its finance division had conducted an “in-depth analysis” of the deal as proposed by Related, and signed off on it before it was approved.

“We took additional time for this analysis, with the goal of protecting the use of taxpayer dollars,” said the spokesman, Rendy Desamours. “It is a fiscally responsible path forward.”