Cable giant Comcast and online search king Google are in talks with Time Warner about making an investment in its America Online unit of as much as $5 billion, according to reports Thursday in The Wall Street Journal and The New York Times, among others.

The move could create a significant rival to Yahoo! and give Google and Comcast access to AOL’s huge trove of customers.

However, Time Warner CEO Richard Parsons dismissed the talks about a possible link-up with Comcast and Google as “a market rumor,” according to a Reuters report Thursday morning.

Details of what a deal might look like are still unclear, according to several press reports, though in one scenario Comcast and Google would own up to half of AOL. Time Warner officials are said to be resistant to the two companies’ owning that large a stake because Time Warner wants AOL-a huge cash flow contributor-to continue to feed the media giant’s bottom line.

The move represents the latest in a string of strategies being engineered by large media companies and software companies to link up at a time when everyone is bullish about broadband content.

Time Warner already has had discussions with software titan Microsoft about a possible investment in AOL in which Microsoft’s search engine would replace Google’s as AOL’s incumbent search service. Those talks apparently prompted Google to step up and consider deepening its relationship with AOL.

Meanwhile, Comcast, which is already the country’s largest broadband provider, sees an opportunity to capitalize on the throngs of people who visit AOL’s Web sites and use AOL’s popular instant messaging service. Further, the move would help Comcast bolster its streaming video business. It could also give the cable company an inside track to capturing AOL’s dwindling number of dial-up customers.