NEW YORK ( TheStreet) -- Hedge fund manager Bill Ackman wants mall operator General Growth Properties ( GGP) to sell itself to Simon Property Group ( SPG) in a prospective $20 billion-plus deal that could be one of the largest U.S. acquisitions since the financial crisis. That's not news -- Ackman unveiled the plans in an August letter -- but the hedge fund manager seems to be prioritizing the proposed deal over other "shakeup" bets he has made in recent history. Speaking at the Value Investing Congress on Monday, Ackman who runs Pershing Square Capital Management, led a keynote presentation by detailing his General Growth M&A efforts, while putting J.C. Penney ( JCP) and Procter & Gamble ( PG) on the bully pulpit backburner. Ackman's fund has put big money behind restructuring efforts at J.C. Penney and calls for management change at consumer products giant Procter & Gamble, amid a heavy slate of 2012 investments. But the clock may be ticking on General Growth much faster, with a rival for the real estate company buying up shares in what Ackman says is an effort to thwart any takeover alternative. Ackman's presentation on General Growth reiterated his goal to sell the mall operator to Simon Property, netting shareholders a premium to what 40%-plus shareholder Brookfield Asset Management ( BAM) would pay for a majority stake. Ackman owns more than 10% of General Growth's shares, making his fund the company's second-largest shareholder. "It is only a matter of time before Brookfield de facto controls the company," warned Pershing in a letter sent to General Growth during the summer. " If control of the company is ceded to Brookfield, shareholders will suffer enormous and irreparable harm for they will lose the ability to capture an appropriate control premium for their shares," he added. In November, Brookfield proposed it buy General Growth and sell off unwanted assets to Simon Property to finance a deal. In April, Pershing says Simon Property rejected the idea of buying assets piecemeal and Brookfield began buying up General Growth shares as investors like Blackstone and Fairholme Funds exited large stakes, according to Ackman's letter. Brookfield has gone from owning 29% of the company at emergence from bankruptcy to 42.2% today. Where does this time-sensitive focus leave Ackman's prod of management at J.C. Penney and Procter & Gamble? There is still work to be done, even if they weren't top of mind at this year's Value Investing Conference.