Pershing Square Capital Management, the hedge fund that had been pushing for General Growth Properties Inc. to sell itself, is switching gears to become a passive investor in the Chicago REIT.

The firm, headed by William Ackman, has agreed to sell $271.9 million of warrants in GGP to Brookfield Asset Management Inc., which in turn has offered to sell them back to the REIT for the same purchase price.

The warrants represent 18.4 million GGP shares, or roughly 2...