Koor and Property and Building agreed to acquire the Fifth Avenue building in late 2009 for $353 million. The deal closed in April 2010.

Most of the building is leased to HSBC under a 10-year contract, Koor and Property and Building, both subsidiaries of IDB Holding Corp , said on Sunday.

The building has existing external financing of $210 million.

The deal is subject to approval by shareholders of both companies as well as the financing bank.