** Shares of real estate developer Howard Hughes HHH.N slip 4.5% to $76.99 in premarket trading
** Bill Ackman's Pershing Square Capital Management on Tuesday revised its offer for stake in HHH, proposing to buy stake worth $900 million vs $1 billion earlier
** Pershing's new proposal is for 10 million newly issued shares and would up Pershing's stake to 48% from 37.6% now
** Earlier proposal in January planned to increase Pershing's stake to between 61%-69%
** New offer price of $90 per share still an 11.7% premium to HHH closing price on Tuesday of $80.60
** Ackman would become chairman and CEO of Howard Hughes under proposal
** HHH says special committee is assessing offer, says has not engaged in negotiations
** HHH shares rose nearly 7% on Tuesday, and is up 4.8% year to date
(Reporting by Lisa Pauline Mattackal)
((LisaPauline.Mattackal@thomsonreuters.com;))