Feb. 11 (Bloomberg) -- Billionaire investor Carl Icahn bought a 2.73 percent stake in Alliance Data Systems Corp., the Dallas-based credit-card processor whose acquisition by Blackstone Group LP has been held up by regulatory issues.

Icahn holds 2.15 million shares including options, according to a filing today with the U.S. Securities and Exchange Commission. Icahn may seek to discuss Blackstone's $6.6 billion bid with the Alliance management, the filing said.

Blackstone, the New York-based leveraged buyout firm run by Stephen Schwarzman, said last month the deal had been delayed because federal bank regulators want it to commit $400 million in financing if Alliance Data's credit-card bank runs into trouble. Alliance Data sued Blackstone, saying it was trying to back out of the deal. The company dropped the suit Feb. 8 after being reassured Blackstone was working to complete the deal.

Alliance rose 31 cents to $55.33 at 4:15 p.m. in New York trading. The stock is 32 percent below Blackstone's $81.75 purchase price.

Icahn paid from $41.84 to $73.42 for the shares, according to the filing. He didn't return a phone call seeking comment.

Icahn's disclosure follows other hedge-fund investors. D.E. Shaw & Co., the New York-based manager that oversees about $35 billion, said last week it bought a 6.6 percent stake in Alliance.

To contact the reporter on this story: Jason Kelly in New York at jkelly14@bloomberg.net

Last Updated: February 11, 2008 17:19 EST