Herbalife Ltd. said it concluded talks that would have taken the company private and simultaneously reached an agreement with billionaire investor Carl Icahn.

Icahn, who has built up his stake to become the nutritional-supplement company’s biggest shareholder in recent years, agreed only to boost holdings past 50 percent if he bought it outright, Herbalife said Monday in a statement. He held about 24 percent of the company as of June.

Herbalife also announced a self-tender offer to buy as much as $600 million of its own shares that comes with a contingent cash payment if Herbalife is acquired in a private transaction within two years.

Shares of the Los Angeles-based company surged as much as 9 percent to $67.50 in early trading Monday. The stock had climbed 29 percent this year through Friday’s close.

Herbalife will pay $60 to $68 per share in the offer, which is scheduled to run through Sept. 19. Icahn and the Herbalife board and executives won’t sell their shares as part of the offer, according to the statement.