Simon Property Group Inc. raised its unsolicited takeover bid for rival mall owner Macerich Co. to about $16.8 billion, calling it a final offer.

Simon, the biggest U.S. mall landlord, offered $95.50 a share, up from $91 on March 9, the Indianapolis-based company said in a statement Friday.

Both companies have a significant presence in the Philadelphia area. Simon has nine area malls, including King of Prussia, Philadelphia Mills, and Oxford Valley. Macerich has agreed to invest more than $100 million in the redevelopment of the Gallery at Market East.

Simon's latest offer will be withdrawn if Simon is unable to meet with Macerich to negotiate terms of an agreement by 8 p.m. Philadelphia time April 1. Simon has said it has made multiple attempts to discuss its interest and Macerich has refused to engage in talks.

"We believe our offer is compelling and will deliver significant and immediate value to Macerich shareholders," Simon chief executive officer David Simon said in the statement. "We encourage the Macerich board to give our proposal the serious consideration it deserves and to take into account the views of Macerich shareholders."

Macerich has taken steps to thwart a hostile takeover. The Santa Monica, Calif.-based real estate investment trust said on March 17 that it was staggering the election of directors, which would make it more difficult to oust the board, and adopting a "poison pill" defense that raises the price Simon would have to pay because more Macerich shares would be issued.

In its own statement, Macerich confirmed it received the new proposal and said its board will review it with its financial and legal advisers.

"At this point it's back in Macerich's court," said Jeffrey Langbaum, a REIT analyst with Bloomberg Intelligence. "Either they say 'OK, let's talk,' or 'No, thank you, that offer's not high enough.' "

Macerich fell 4.6 percent to $89.21 on Friday, indicating investors expect a deal won't be reached. Simon has been the only company to publicly make a bid.