Terms of Icahn's bid offers $30 per share in cash for CVR, a premium of 8.7% over the target's Wednesday close, and also would provide shareholders a contingent value right that would give current investors a share of the gain should Icahn flip CVR to another buyer within nine months of closing his deal. The offer, which is set to expire on our around March 23, requires at least 35.76% of the company's shares to tender.

Icahn, who also said he would nominate a slate of nine directors to CVR's board, in a regulatory filing late Thursday, Feb. 17, was clear he is making the bid in hopes of forcing a sale process. The billionaire activist investor said that if the current board puts CVR up for sale before the tender expires, he reserves the right to withdraw the tender and the proxy fight.

"We are launching this tender offer and proxy fight to provide shareholders the opportunity to obtain the value that we believe can be obtained in a sale of the company," the investor said. This is a win-win-win for shareholders."

Icahn, who through affiliates owns about 14.54% of Sugar Land, Texas-based CVR, turned up the heat on the company earlier this week after CVR said it intends to sell a majority stake in its nitrogen fertilizer unit and institute a dividend. Icahn rebuffed those moves as insufficient, and urged the small company to find a larger refiner partner.

CVR responded by saying it remains "confident about the company's prospects under our long-term growth strategy." The company in a Thursday statement acknowledged the receipt of Icahn's notice, and said the board would review the actions and "respond as appropriate in due course."

In offering to buy CVR, Icahn is repeating a strategy he used unsuccessfully last year when he tried to flush out buyers for both Clorox Co. and Commercial Metals Inc. The investor said he believes CVR could fetch at least $37 per share in a sale, and listed Western Refining Inc., HollyFrontier, Tesoro Corp., Valero, Marathon Petroleum Corp. and ConocoPhilips as potential buyers.

The investor said he will initiate dialogues with a number of potential acquirers in the coming weeks to gauge their interest in a CVR deal.

Deutsche Bank AG's Rob Wheeler and Greg Sommer and Goldman, Sachs & Co.'s Bill Anderson and Andy Orekar are advising CVR Energy, A Wachtell, Lipton, Rosen & Katz team led by Andy Brownstein is serving as legal counsel.

- Claire Poole contributed to this report