WASHINGTON - TWO of the largest online health companies in the US announced on Friday that they were joining forces to take on the leader in the field of Internet medical advice, WebMD.com.

New York-based Waterfront Media and Washington-based Revolution Health Network said the boards of directors of the two companies had unanimously approved the merger.

They did not disclose terms of the agreement.

The deal calls for the websites run by Revolution Health to become part of Waterfront Media's Everyday Health Network, the companies said in a statement.

Waterfront Media co-founder Benjamin Wolin will be chief executive of the new company while Revolution Health founder Steve Case will join the board of the new firm.

'The inclusion of Revolution Health and its properties in the Everyday Health Network creates the most powerful, expansive online health experience for consumers,' said Mr Wolin.

Mr Case, a co-founder of America Online, said 'the merger of Waterfront Media and Revolution Health Network builds on each company's complementary strengths to create a new industry powerhouse.'

Waterfront Media operates more than 20 online health sites including EverydayHealth.com, WhatToExpect.com and SouthBeachDiet.com.

Revolution Health's websites including RevolutionHealth.com, HealthTalk.com and CarePages.com.

According to comScore Media Metrix figures, Everyday Health had more than 14 million unique visitors in Aug while Revolution Health Network had over 12 million. WebMD had 17.7 million unique visitors that same month. -- AFP