The Wall Street Journal has word from two private-equity firms that Google is interested in purchasing the "core business" of its rival Yahoo--a move that could put it up against other tech giant, Microsoft, in its bid for the company. Though the move is still in its "early-stage discussions" and no formal bid has been put together, The Journal lays out the case for why the move could be a win for Google.

Google is interested in selling some advertising across Yahoo's websites—something Yahoo largely does on its own today—according to people familiar with the matter.

Any deal involving Google could also bring other opportunities, such as bring Google's social-networking service Google+ to Yahoo's audience of nearly 700 million unique visitors a month, these people said.

Yahoo also has relationships with many so-called premium content publishers such as ABC News, which provides video and other content for Yahoo sites and for which Yahoo currently sells ads. Google is interested in having deeper business relationships with such publishers, one of these people said.

Of course, in addition to Microsoft's joint bid at the company, the same anti-trust concerns that stopped an "advertising partnership" between Google and Yahoo in 2008 could stymie the search company's efforts, The Journal reports.