July 21 (Reuters) - Time Warner Inc's board moved to prevent its shareholders from calling special meetings, effectively throwing up a hurdle to any quick move to approve a potential takeover by Rupert Murdoch's Twenty-First Century Fox .
Fox made an offer for Time Warner for about $80 billion or about $85 per share in a mix of stock and cash that Time Warner rebuffed, both companies disclosed last week.
Time Warner previously allowed as few as 15 percent of its shareholders to call a special meeting, factors that could help a takeover bid. The move is temporary however, as the board said it plans to reinstate the special meeting provision during its 2015 annual meeting, according to a regulatory file on Monday.
A spokesman for Time Warner, which owns cable networks TNT and CNN, pay-TV channel HBO and Warner Bros movie studio, declined to comment.
Time Warner Chief Executive Jeffrey Bewkes told his employees in video that the company's standalone strategic plan would create value "superior to any proposal" that Fox could offer.
Part of the issue involves the mix of cash and stock and lack of control of Time Warner's shareholders if a deal should go through, sources told Reuters last week.
Murdoch controls Fox through a 39 percent stake in special shares that were not part of the offer.
Fox offered 60 percent in common stock and 40 percent cash.
Several Time Warner shareholders told Reuters last week that Fox may have to raise the bid to as much as $95 a share boosting its cash component to seal a merger.
(Reporting by Jennifer Saba in New York; Editing by Bernard Orr)