Billionaire corporate raider Carl Icahn has upped his offer to Lions Gate Entertainment (NYSE: LGF), offering to acquire all of the studio’s outstanding shares.

"The Icahn Group is now offering to purchase UP TO ALL of Lions Gate's outstanding common shares," the investment company said in a release on Friday. "In addition, the expiration date of the Offer has been extended to April 30, 2010."

A representative for Lionsgate did not immediately return a request for comment.

The offer comes on the very day that Lionsgate is poised to bid in the final round of the expected sale of MGM, a deal that Icahn opposes. Lionsgate has been struggling with what price to set for the debt-laden MGM, and is bidding against better-funded and larger rivals, Time-Warner and Access Industries.

Last week, the studio rejected Icahn’s offer to acquire 13.2 million shares -- about 30 percent of Lionsgate -- for $6.00 per share, or $79,986,520. Now, Icahn is offering to buy at least 50.1% of Lionsgate's common shares, which would give him full control.

Lionsgate said Icahn’s initial offer was 28.5 percent less than what Wall Street analysts have said its shares are worth. Shares of Lionsgate stock were trading at $6.00 Friday morning, up about half a percent.

Meanwhile, it was not entirely clear what strategy Icahn was pursuing, and why he felt shareholders that did not sell to him previously would now do so. (A representative for Icahn declined to comment.) He currently owns 18.9 percent, and has sought seats on the board, which so far Lionsgate has not granted him.

Lionsgate has proposed that its shareholders adopt a defensive rights plan, or poison pill, to keep Icahn from accumulating shares.

Icahn said on Friday that he intended to pursue legal action against Lionsgate's poison pill. If his offer is successful, his firm, the Icahn Group, would replace the studio's board of directors with its own nominees, he said.

In rejecting Icahn's earlier offer, Lionsgate said that the Icahn Group "has limited experience in operating a business in Lionsgate’s industry."

“Despite this, the Icahn Group is seeking a greater opportunity to participate in decisions regarding major acquisitions and other matters that would affect shareholders.”

The studio’s board of directors voted unanimously against the unsolicited offer, calling it a "partial bid," “financially inadequate,” “coercive” and “not in the best interests of Lionsgate and its shareholders and other stakeholders.”

"Lions Gate previously criticized our tender offer for being partial," Icahn said Friday. "That is no longer the case."

Here's the press release from the Icahn Group: 

Icahn Announces Amendments to Tender Offer for Common Shares of Lions Gate Entertainment Corp.

NEW YORK, March 19 /PRNewswire/ -- Carl C. Icahn announced today that the offer (the "Offer") by certain of his affiliated entities (the "Icahn Group") to purchase up to 13,164,420 common shares of Lions Gate Entertainment Corp. ("Lions Gate") has been amended to provide that the Icahn Group is now offering to purchase UP TO ALL of Lions Gate's outstanding common shares.