Billionaire US investor Carl Icahn has accused media giant Time Warner of not doing enough for its shareholders.
Time Warner says it will meet with Mr Icahn
Mr Icahn said he wants the world's biggest media company to separate its cable business and buy back at least $20bn (£11bn) of its stock.
Owning more than 120 million shares in the firm, in association with a number of hedge funds, Mr Icahn said he wanted to meet company boss Richard Parsons.
Time Warner said it would see Mr Icahn and was committed to its shareholders.
Mr Icahn said that while Time Warner managers had done a "commendable job managing each of their various businesses", not enough was being proposed to enhance the return for shareholders.
The company, which owns Warner Brothers movie studio and cable news channel CNN, is currently timetabled to buy back $5bn of its shares over the next two years.
"Our board and our management are committed to creating long-term value for all shareholders and we've been on a course that demonstrates that commitment," said a company spokesman.
The billionaire's comments come two weeks after the company announced second quarter losses of $321m, compared to a $77m net profit for the same period in 2004.
The losses were caused by Time Warner having to settle a $2.4bn shareholder lawsuit, after investors accused it of overstating revenue from 1999 to 2002.
Mr Icahn has a history of calling for changes at the companies in which he invests, such as forcing Texaco into bankruptcy proceedings back in 1987.
The 26th richest person in the world according to Forbes magazine, Mr Icahn was in May appointed chairman of US video rental giant Blockbuster.