Barry Diller's People Inc. is preparing a bid to buy casino giant MGM Resorts, a deal that would value it at more than $18 billion, CNBC's Andrew Ross Sorkin reported Monday.

The proposal has not yet been finalized, though the company is planning an offer of $48.30 per share in cash, Sorkin reported. MGM is the company behind major Las Vegas properties including Bellagio and Aria.

MGM's stock was up roughly 14% in premarket trading Monday. Shares of Diller's firm were up 4% premarket.

Diller already sits on the board of MGM Resorts and would recuse himself from any board vote on a potential deal, Sorkin reported.

People Inc., formerly known as IAC, owns a roughly 26.1% stake in MGM. The bid could come as early as Monday.