Grab Holdings is in talks to go public through a merger with a special purpose acquisition company that could value the ride-hailing giant at nearly $40 billion, making it the largest ever blank-check deal, people familiar with the matter said on Thursday.

The Wall Street Journal reported earlier in the day SoftBank-backed Grab was in talks with Altimeter Capital Management LP.

Grab is expected to raise between $3 billion and $4 billion from private investors, according to the report.

Reuters first reported in January, citing sources, that Singapore-based Grab was exploring a listing in the United States.

Silicon Valley-based venture capital firm Altimeter has backed two SPACs — Altimeter Growth Corp and Altimeter Growth Corp 2. The WSJ report did not specify which of the two SPACs Grab was in talks with.

Special purpose acquisition companies, or SPACs, are shell companies that raise funds through an initial public offering to take a private company public.

Other recent large SPAC deals include UMW Holdings Corp's $16-billion merger with a blank-check firm backed by billionaire Alec Gores, and the $24-billion deal that luxury electric vehicle maker Lucid Motors struck with a Michael Klein-backed SPAC.

Altimeter did not immediately respond to a Reuters request for comment, while Grab could not be reached for comment outside regular business hours.