NEW YORK (AFP) - Media tycoon Rupert Murdoch said on Tuesday his 21st Century Fox group had withdrawn its bid for Time Warner, a massive offer which could have shaken up the media-entertainment world.

Worth an estimated US$80 billion (S$100 billion), the offer was taken off the table after Time Warner "refused to engage with us" and the news hurt the share price of 21st Century Fox, Murdoch said.

"The reaction in our share price since our proposal was made undervalues our stock and makes the transaction unattractive to Fox shareholders," he said, in a statement.

"These factors, coupled with our commitment to be both disciplined in our approach to the combination and focused on delivering value for the Fox shareholders, has led us to withdraw our offer." Murdoch said he made the decision even though the deal "had significant strategic merit and compelling financial rationale and our approach had always been friendly". The statement said the board authorised a US$6 billion share repurchase programme after withdrawing the offer.

The bid unveiled by 21st Century Fox in July would have merged two of the world's biggest media-entertainment empires.

It would combine the storied Hollywood studios of Time Warner and 20th Century Fox, and join Time Warner's big cable channels such as HBO and TBS to Murdoch's Fox sports, news and entertainment channels.

A source familiar with the talks told AFP last month that Murdoch's group wanted to buy Time Warner and then spin off CNN, which is the cable news rival to his Fox News Channel.

Time Warner said it the time it had rejected the offer and would not pursue talks.

The offer came amid a shifting media landscape after both conglomerates spun off their slow-growing publishing operations and established companies focusing on film, television and other high-growth segments.

Murdoch last year broke up his media empire into two firms: 21st Century Fox and News Corp, which operates The Wall Street Journal, and newspapers in Britain and Australia. Time Warner this year spun off its magazine unit Time, which publishes its flagship news weekly and other titles including Sports Illustrated and People.