Media tycoon Rupert Murdoch has indicated he won't bid for the newspaper group that includes the Los Angeles Times, saying he would be barred under US cross-ownership rules.

Murdoch made the comments on Twitter on Thursday, just days after Tribune Co. approved a spinoff of its newspaper division -- including the big Los Angeles Times and Chicago Tribune dailies -- for August 4.

"Sorry can't buy Trib group or LA Times - cross-ownership laws from another age still in place," he tweeted.

US regulators have for now put off discussion on easing the rules that bar ownership of both television stations and newspapers in the same markets.

Murdoch last year split his empire into two firms including News Corp, which operates the Wall Street Journal and other newspapers around the world, and the television-film group 21st Century Fox.

US rules would likely bar Murdoch from owning newspapers in Los Angeles and Chicago where he already has television properties, although he did obtain a waiver to operate the New York Post.

Murdoch was widely believed to be interested in the Los Angeles Times, and some reports said he was willing to buy the entire group to get that daily.

Murdoch's 21st Century Fox said this week it made an unsuccessful bid for rival Time Warner which could shake up the media-entertainment world.

The bid by 21st Century Fox, which would merge two of the world's biggest media-entertainment empires if allowed to proceed, was for $80 billion, according to sources.