WASHINGTON — New York City Mayor Zohran Mamdani met Thursday with President Donald Trump to propose a more than $21 billion federal investment to build 12,000 affordable housing units over Sunnyside Yard in Queens, City Hall announced.

The proposal calls for constructing what officials described as the world’s largest deck over the rail yard — the busiest in North America — to support 12,000 new homes, including 6,000 Mitchell-Lama-style units. The plan also envisions creating 30,000 union jobs and adding parks, schools and health care clinics.

If approved, the project would represent the largest housing and infrastructure investment in New York City in more than 50 years, according to the mayor’s office.

“New York City is facing a generational affordability challenge,” Mamdani said in a statement. “Working families are being priced out of the neighborhoods they built. To meet this moment, we need a true federal partner prepared to invest boldly and act urgently.”

City officials said the mayor also stressed the need to strengthen financing tools for affordable housing, preserve public housing and modernize regulatory processes to accelerate construction while maintaining labor standards and community input.

Both sides agreed to continue discussions in the coming weeks, the mayor’s office said.