Blackstone Group said it has agreed to acquire Hilton Hotels Corp. for about $26 billion, including the assumption of debt.

Blackstone said it will pay $47.50 a share in cash, a 40 percent premium over Hilton's closing price on Monday. The cash portion amounts to $18.5 billion, and Blackstone agreed to shoulder Hilton's $7.5 billion in debt.

Hilton's board approved the transaction on Tuesday, Blackstone said. In a statement, Hilton chief executive Stephen F. Bollenbach said the board was swayed by Blackstone's "significant premium."

Blackstone said it already owns more than 100,000 hotel rooms in the U.S. and Europe, including its La Quinta Inns and Suites chain to LXR Luxury Resorts and Hotels.

Acquiring Hilton will let it add the Hilton chain as well as Conrad Hotels & Resorts, Doubletree, Embassy Suites, Hampton Inn, Hilton Garden Inn, Hilton Grand Vacations, Homewood Suites by Hilton. It also includes the Waldorf-Astoria in New York.

Blackstone said a special meeting of Hilton shareholders will be scheduled soon, to give them a chance to vote on the offer. It added that it expects the deal to close by the end of the year.