CUPERTINO, Calif. ( TheStreet) -- Apple ( AAPL) is negotiating for Microsoft's ( MSFT) Bing to replace Google ( GOOG) as the default search engine on Apple's iPhone, BusinessWeek reports, citing two sources familiar with the matter. The talks have been underway for weeks, the sources said. The discussions reflect the accelerating rivalry between Apple and Google, who have worked as partners in the past. Google CEO Eric Schmidt once had a seat on Apple's board; he resigned in August. Microsoft's Bing search engine, which debuted last year, is looking to gain market share from Google, the leader in Internet search. "Apple and Google know the other is their primary enemy," one of the people familiar with Apple's thinking told BusinessWeek. "Microsoft is now a pawn in that battle." Microsoft also may be lobbying to make Bing an alternative on Apple's Safari browser for Mac users, according to the report. Currently, Mac users can choose either Google or Yahoo! ( YHOO) search through the Safari browser.