In what could be its first major investment deal on the Internet to date, News Corp. is close to shelling out at least $500 million in cash and assets to buy a stake in medical Web service provider Healtheon/WebMD Corp., in order to provide health information and services through the media conglom’s television, cable and future Internet properties.

Until now, News Corp. has been operating without a pulse on the ‘Net. But under terms of the Healtheon/WebMD pact, which is expected to be finalized in the next two weeks, News Corp. plans to invest $150 million in cash for a 10% stake in Healtheon/WebMD, valuing its shares at $50. Healtheon’s stock closed at $37.13 on Friday.

News Corp. will also invest $150 million in Healtheon WebMD Intl., a new subsid, in exchange for a 50% stake in the venture.

News Corp. will distrib programming from the Web site on its Health Network cable channel and promote the sites on the Fox network and other media outlets. The cabler could also become part of Healtheon WebMD Intl.

Negotiations have been taking place between News Corp. chairman Rupert Murdoch and the Web companies for the past six weeks in London, New York and Los Angeles.

The deal is not expected to be announced until Healtheon Corp. (founded by James Clark, who helped create Web browser powerhouse Netscape Communications) completes its merger with WebMD Inc. Merger is skedded to close on Thursday.

Healtheon is buying Atlanta-based WebMD for around $5 billion to form the largest online company linking doctors with insurers, suppliers and patients. The combined outfit will also acquire the outstanding stock, options and warrants of closely held Greenberg News, which provides medical news and analysis over its Medcast Networks.

The potential News Corp. deal follows Murdoch’s announcement last week that the conglom will take strategic stakes in “innovative” new-media companies.

News Corp. will “aggressively establish new platforms” such as interactive TV, Murdoch said, praising the turnaround of TV Guide as “one of the company’s most exciting investments.”

The deal with Healtheon would not only boost News Corp.’s online activities, but also provide a Web partner to Health Network, which launched in July to 17 million cable subscribers.

Health Network replaces AHN (America’s Health Network) and News Corp.’s Fit TV, which merged earlier this year as part of a plan to funnel their subscribers to a successor network.

CBS Corp. has also invested heavily in medical Web sites, having acquired stakes in online pharmacy Rx.com and launched a co-branded site with Medscape Inc.

CBS bought a 35% stake in the latter in July for $150 million in promotions through CBS’ TV, radio and billboard properties over the next seven years.

Spokesmen from News Corp. and Healtheon declined to comment.