Microsoft has been trying to buy and muscle its way into the online advertising business, but it may soon add one additional tactic to its toolbox -- trading. According to a report in AdAge, Microsoft could be looking to sell Avenue A | Razorfish or trade the agency to WPP in exchange for portions of the holding company's 24/7 Real Media business.

Under the terms of the rumored deal, WPP would get Avenue A, while Microsoft would get 24/7 Real Media's Open AdStream publisher ad-serving tool.

But WPP may not be the only contender for Avenue A. While Microsoft and WPP have had recurring talks on and off for the past six months, Microsoft has had a hard time finding a buyer willing to pay what it spent on the agency. Microsoft first acquired Avenue A when it purchased aQuantive last year for $5.9 billion. That deal gave Microsoft Atlas, DrivePM and Avenue A.