A Qatari buyer is looking to combine multiple apartments at the ultra-luxe 220 Central Park South into a single, $250 million penthouse in the sky, sources told The Real Deal. If a deal is finalized, the mystery buyer would own the priciest residence in New York City by far, and one of the world’s most expensive homes.

It wasn’t immediately clear which units are being combined. A representative for Corcoran Sunshine, which is marketing the project’s 118 condominiums on behalf of developer Vornado Realty Trust, declined to comment.

The Robert A.M. Stern-designed building’s latest condo offering plan includes seven penthouses. Two of them, Penthouses 75 and 76, don’t have a price tag, leaving open the possibility that they could be combined into a single unit of nearly 14,000 square feet. The other five penthouses, all ostensibly on lower floors, have price tags of more than $50 million. Penthouse 73, which spans over 9,500 square feet, is the most expensive unit currently listed, at $100 million, but sources said that pad is already in contract.

The buyer, developer and architect are still hammering out details of the combination, a source familiar with the project said.

The price would easily shatter the New York record set by a penthouse at Extell Development’s One57, which sold for $100.5 million in January. The city’s priciest apartment entering the market is the penthouse at the Chetrit Group’s Sony Building conversion at 550 Madison Avenue, which will ask $150 million, according to a condo offering plan first reported by TRD. The priciest current listings in the U.S. are the Ziff estate in Manalapan, Florida, and the Palazzo di Amore mansion in Beverly Hills, tied at $195 million.

The price could even break the record 140 million pounds ($237 million at the time, $220 million in today’s exchange rate) an unnamed buyer paid for a penthouse in the London luxury apartment building One Hyde Park in early 2014.

Sales at 220 Central Park South have been strong, defying industry talk over a slowing ultra-luxury market. In May, Vornado announced it had sold units in the building for a combined $1.1 billion in just six weeks.

“We’re delivering the best product that’s ever been delivered in the Manhattan residential market,” CEO Steve Roth said at the time. “We’re going to get a fair price for a fair product.” The building’s total sellout is projected at $2.84 billion.

Qataris have been active investors in New York luxury real estate in recent years. In 2012, Qatar’s Prime Minister Sheikh Hamad bin Jassim bin Jaber Al-Thani paid Aby Rosen $47 million for his townhouse at 22 East 71st Street. A year later, he paid $35 million for a six-bedroom townhouse at Beekman Place. And in 2014 the Qatari government briefly entered contract to buy a townhouse at 19 East 64th Street, before walking away from the deal.