NEW YORK -- U.S. hedge fund Greenlight Capital filed suit against Apple (IW 500/9) Thursday as part of efforts to compel the tech giant to give shareholders more of its huge cash stockpile.

Apple responded by saying it has been "in active discussions about returning additional cash to shareholders."

Greenlight sued the maker of iPhones and iPads to block a shareholder vote that includes a proposal supported by management to make it impossible for the Apple board to decide to issue preferred stock without shareholder approval.

Greenlight said in a letter to shareholders it wants Apple to issue "perpetual preferred stock" to distribute a bounty from the $137 billion cash the company is holding.

Apple, which has reclaimed the title of largest U.S. company by market capitalization and which rose nearly 3% Thursday, pledged to evaluate the Greenlight proposal.

"As part of our review, we will thoroughly evaluate Greenlight Capital's current proposal to issue some form of preferred stock," Apple said in a statement.

"We welcome Greenlight's views and the views of all our shareholders."