Billionaire investor Bill Ackman's Pershing Square Capital Management said on Tuesday it would buy 10 million newly issued shares of Howard Hughes Holdings for $900 million as it revised its proposal to the real estate developer.

Pershing Square submitted a new non-binding offer to increase its stake in Howard Hughes Holdings through a $900 million investment that would make Bill Ackman the new chief executive of the real-estate company.

Howard Hughes Holdings (HHH) shares retreated 8% in Wednesday late morning trading, wiping out Tuesday's 6.8% gain, after confirming a revised takeover proposal from billionaire investor Bill Ackman's Pershing Square Capital Management.