TORONTO (AP) — Brookfield Asset Management is responding to activist investor William Ackman letter that urges the mall operator's board to consider a possible sale of the company before Brookfield acquires enough shares to take control of it.

Brookfield said in a release it is not moving to acquire the company and has no interest in selling its roughly 40 percent stake.

In a letter to General Growth Properties' board released Thursday, Ackman, of Pershing Square Capital Management, said he is concerned that Brookfield will soon acquire enough shares to take the company over, without paying other shareholders a fair price. Pershing owns about 10.2 percent.

Brookfield owned 29 percent when General Growth emerged from bankruptcy protection three years ago.

General Growth filed the largest real estate bankruptcy case in U.S. history in 2009. It exited with aid from an investor group led by Brookfield, which manages a range of utility, infrastructure and real estate assets.