NEW YORK (CNN/Money) - Online search company Google and Comcast, the nation's leading cable company, are in negotiations with Time Warner to purchase a stake in its America Online unit, according to a source close to the situation.

News of the talks, first reported in The Wall Street Journal Thursday, comes as Time Warner (Research) is also discussing a joint venture between AOL and Microsoft's MSN unit, the source told CNN/Money. (Time Warner also owns CNN/Money.)

The source, who requested anonymity, said that Google and Comcast's discussions with AOL are in early stages and that a deal is not imminent.

Spokespeople for Time Warner and Comcast (Research) refused to comment about the negotiations and a spokesperson from Google (Research) was not immediately available for comment.

At a luncheon in Hong Kong Thursday, Time Warner CEO Dick Parsons declined to confirm the negotiations, Reuters reported. "It's market rumors, and I can't curb market rumors," he was quoted as saying.

AOL, which has suffered subscriber losses in its core dial-up Internet access business during the past few years, has recently become a more interesting property for other media and technology companies because of its online content, according to analysts.

The surge in online advertising has also helped boost the unit's fortunes recently. Although AOL's overall sales dipped by 4 percent in the second quarter, advertising revenues were up 45 percent from a year ago and operating income increased by 33 percent.

News of the negotiations comes on the heels of continued pressure by corporate raider Carl Icahn on Time Warner to take steps to boost its stock price. (See story.)

Shares of Google, Comcast and Time Warner all fell more than 1 percent on Wednesday.

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