Murdoch: Will I be fit to run my empire in 10 years'?

Rupert Murdoch has conceded for the first time that he will not be able to run News Corporation forever after revealing his wife Wendi Deng is expecting his sixth child in the summer.

"I don't know what the time frame will be. Will I be as fit, as intelligent and mentally agile as I am today in 10 years? That's a lot to expect," said Mr Murdoch, who will then be 81.

"If I feel that way, I'll stay on. On the other hand, if they knock on the door and say, Dad, you're losing it - which they would not shrink from - I'll go," he added in unpublished extracts from an interview with US magazine Fortune.

His remarks come as News Corp in New York confirmed reports in Fortune that Mr Murdoch's 35-year-old wife is expecting her second child this summer. A spokesman said: "Yes, it is true."

Mr Murdoch said he was determined to stay on at News Corp for as long as possible to keep the company on an even keel and complete the takeover of US satellite broadcaster DirecTV.

"We're running a very conservative ship at the moment. We're not in the business of deals at the moment. Except for one," he said.

"That'll be the big exception. And the Dodgers [the LA baseball team News Corp wants to sell]. I don't think owning teams is something for big corporations," he told Fortune.

The "one" deal he referred to is believed to be DirecTV, which he has been battling to control for the past two years.

If he takes control of DirecTV or alternatively swallows up Echostar, the rival US bidder for DirecTV, Mr Murdoch will fulfil a long held ambition to own a broadcasting network that spans the globe.

Mr Murdoch is optimistic News Corp will ride out the current downturn without the huge problems faced by the likes of AOL Time Warner and Vivendi Universal and there will be further improvement after a possible war with Iraq is over.

"We're keeping our heads down, managing the businesses, keeping our profits up. Who knows what the future holds," he said.

"I have a pretty optimistic medium and long-term view but things are going to be pretty sticky until we get Iraq behind us.

"But once it's behind us, the whole world will benefit from cheaper oil, which will be a bigger stimulus than anything else."

Mr Murdoch has previously declared he will go on working until "I am 100".

He recently hinted that, when he does go, he expects sons Lachlan and James to share the News Corp leadership, with the chief operating officer, Peter Chernin, also playing a crucial role.

Today's news that Mr Murdoch is expecting another child will renew speculation over the future leadership of News Corp.

However, he insisted he was fighting fit and likely to go on for some time, adding he and his wife were "thrilled" at the news.

Fortune journalist Marc Gunther also asked Mr Murdoch whether his recent appearance in an Australian-made documentary, in which he pumped iron and declared proudly he had 0% cholesterol, was just for show.

Mr Murdoch was matter of fact: "I do it [work out] every day, or at least six days a week.

"I'm making everybody else do it, too. It's a massive gymnasium, built at considerable cost," he told Fortune, referring to a new gym on the third floor of the News Corp headquarters in New York.

Mr Murdoch was also asked about editorial interference at the Sun. He said the new editor, Rebekah Wade, had visited him two weekends ago to discuss a range of issues, including pricing and promotion.

The pair had disagreed strongly over the editorial line the paper should take on the subject of university tuition fees.

"Murdoch told me he thought the government should be charging fees but Wade said no, it was wrong, and he deferred to her on that. That was his way of explaining how the paper is independent of him," said Gunther.

Mr Murdoch said: "I enjoy the Sun. I enjoy the vigor of it. I enjoy the cheekiness. I'm proud of the fact they have 10 million readers every day.

"We saved the Times from extinction. The Sunday Times is now more than viable."

The media mogul said he could argue with the taste of some of the stories that appeared in the Sun but added he could say the same of any broadsheet.

"The so-called elitist papers just use a smaller typeface," Mr Murdoch said.

"We want to do both jobs very well. You might say elite and mass rather than high and low."