Paramount Group Inc., a U.S. office landlord, filed for an initial public offering that is poised to be the largest ever for a real estate investment trust.

The New York-based company plans to raise more than $2.5 billion in the stock sale, according to people familiar with the matter who asked not to be identified because the information is private. A filing by the company last week didn’t give a price range or number of shares to be sold. Paramount last month filed a confidential registration statement with the Securities and Exchange Commission.