Broadening its relationship with leading Internet service America Online, CBS said Tuesday that it has inked a $21 million deal under which its MarketWatch.com Web site will serve as the premier business news provider across AOL’s services.

Under terms of the three-year cash and promotions deal, MarketWatch will become an anchor tenant across AOL’s online business areas, including its flagship service that reaches 18 million users, as well as the company’s AOL.com and Netscape Netcenter portals.

Advertising coin

The two companies will split ad revenues.

The deal also calls for the creation of several links from AOL to a joint CBS MarketWatch/AOL site. The two companies will conduct online polls to be used in upcoming CBS MarketWatch TV and radio programming.

The pact extends an already strong alliance that CBS and AOL have maintained since 1995. CBS already distributes content from its news division on AOL; CBS’ SportsLine USA serves as an anchor tenant in AOL’s sports arena; and CBS is also pushing its new fall lineup on the service; the move proved successful last year.

Separately, AOL and China.com said they have launched AOL Hong Kong amid concerns over the Chinese government’s threat to enforce a ban on foreign investment in Web-based ventures on the Chinese mainland.