Blackstone’s Black Hawk consortium has upped its cash offer to buy Sam Zell’s Equity Office Properties to $55.50 a share, it emerged this morning.

The revised bid, which values the company at $39bn, was lodged just a day before EOP’s shareholders gather to vote on what would be the world’s biggest ever property takeover and follows the $56 cash and stock offer submitted by Vornado’s Dove Parent group on Sunday.

Blackstone looked certain to close the takeover of the US’s biggest office landlord after making an initial $54-a-share offer which was recommended by the EOP board late last year.

But Dove Parent, which also comprises Starwood Capital Group and Walton Street Capital, appears equally determined to win the battle for EOP despite an increase the break fee payable to Blackstone to $720m from $500m. Analysts predict that if the shareholder vote tomorrow proves inconclusive, the Dove Parent trio could register yet another counter bid.

In an attempt to improve its standing against Blackstone’s all-cash offer, Vornado offered on Sunday to accelerate its payment, paying $56 a share in cash for 55% of the company in about two months and paying the 45% balance in stock when the merger closes.