It was not immediately clear whether the bid would have any effect on its efforts in Rhode Island. A related constitutional amendment that will appear on November's statewide ballot does not specifically name Harrah's.

The private-equity firms are offering $81 per share in cash, a 22 percent premium to Harrah's closing stock price on Friday on the New York Stock Exchange. After the news, Harrah's shares surged $9.19, or 14 percent, to $75.62 in early trading on the New York Stock Exchange.

Harrah's said it has established a special committee of independent directors to review the offer and has retained UBS Securities LLC as an adviser.

Extra: Read more about the casino debate in Rhode Island.

Harrah's is the world's largest casino company. It operates about 40 casinos, including Caesar's Palace in Las Vegas, its namesake chain, Bally's, Horseshoe, Showboat and other brands throughout the country. The Las Vegas-based company beefed up its portfolio with last year's purchase of Caesars Entertainment Inc.

Also today, Harrah's said it entered a deal with a unit of Boyd Gaming Corp. to exchange about 24 contiguous acres that Harrah's controls on the Las Vegas Strip for Boyd's Barbary Coast Hotel and Casino. Financial terms for that deal were not disclosed.

The real-estate transaction is expected to close in the first quarter of 2007, subject to customary closing conditions, including government approvals. Boyd said it expects to see a non-cash gain of about $280 million in the quarter the deal closes.

-- staff and wire reports