Rupert Murdoch’s 21st Century Fox is abandoning its attempt to take over Time Warner in a proposed deal that would have combined two of the world’s biggest media companies.

The about-face announced Tuesday comes three weeks after Time Warner Inc. revealed that it had rejected 21st Century Fox’s unsolicited $76 billion buyout offer.

Murdoch, a voracious dealmaker throughout his colorful career, had envisioned creating a movie-and-television powerhouse by devouring Time Warner. Twenty First Century Fox owns the 20th Century Fox movie studio, Fox broadcast network, and cable-TV channels Fox News and FX while Time Warner’s stable includes the Warner Bros. movie studio and TV channels such as TNT, TBS and HBO.

There had been hopes on Wall Street that Murdoch wanted Time Warner so badly that he would raise 21st Century Fox’s original cash-and-stock offer bid of roughly $86 per share to as much as $100 per share to win over Time Warner.

Some analysts had expected Murdoch to continue stalking Time Warner, reasoning that the billionaire viewed a takeover as an opportunity to gain a better bargaining position to sell its video content at a time when video distributors are muscling up too.

Comcast Corp., the largest cable and high-speed Internet provider, is trying to win approval to buy rival Time Warner Cable while AT&T Inc. is trying to gobble up satellite TV service DirecTV.

But 21st Century Fox would have had to navigate potentially daunting antitrust hurdles to buy Time Warner. Cultural clashes also loomed had the two companies combined, a factor that turned Time Warner’s merger with AOL Inc. in 2001 into a monumental flop. Time Warner and AOL eventually split, but not before costing their shareholders tens of billions of dollars.

Time Warner had made it clear that it intended to staunchly resist Murdoch’s overtures.

In a Tuesday statement, Time Warner sought to reassure its shareholders. "We look forward to continuing to deliver substantial and sustainable returns," the New York company said.

In his own statement, Murdoch said his New York company’s "future has never been brighter."

With the proposed Time Warner deal off the table, 21st Century Fox’s board approved a plan to spend $6 billion on buying back stock.

Murdoch cited a decline in the New York company’s stock price since the takeover bid was announced as one of the reasons for the change of heart. Fox’s shares have dropped 11 percent. They rose $2.49, or 8 percent, to $33.79 in extended trading Tuesday.

Meanwhile, investors betting that Murdoch was going to sweeten his offer bailed out of Time Warner. Its stock fell $8.39, or nearly 10 percent, to $76.80 in extended trading. Even with Fox out of the picture, Time Warner’s stock remains above its price before Murdoch’s interest was revealed.

This isn’t the first time that Murdoch has walked away from a deal that he once seemed to prize. In 2008, he gave up on buying DirecTV in 2008 through another company, News Corp., after Liberty Media Corp. chairman John Malone outmaneuvered him. He also withdrew a bid to boost News Corp.’s stake in British Sky Broadcasting Group PLC in 2011 amid outrage over a phone hacking scandal at News Corp.’s British newspapers.

Murdoch’s News Corp. split into two companies last year: The newspaper and publishing portion, still called News Corp., and the film-and-TV unit, 21st Century Fox Inc.