According to Investor’s Business Daily, AOL and Microsoft are working on a Web ad service that would compete with Google’s service. The announcement is expected to come by the third week of December according to news reports.

In light of the new reports, many industry watchers no longer expect Time Warner to unload a big piece of America Online.

Even so, rumors had circulated since September that Time Warner wanted to sell a stake in AOL or create a joint venture with Microsoft, Google or Yahoo. Yahoo is believed to have dropped out of talks with Time Warner earlier this year.