US shopping center operator Macerich Co. erected defenses Tuesday against the hostile takeover bid by the mall industry's top power, Simon Properties.
Macerich's board of directors declared that Simon's "coercive" $16 billion, $91 a share offer made last week "substantially undervalues" the company.
It also alleged that Simon's proposal, which would involve selling off some Macerich assets to a third company, General Growth Properties, amounts to "a concerted effort by the two largest companies in the industry to acquire the number three company."
As such the deal proposed on March 9 raises "serious" antitrust issues, the Macerich board said.
Macerich's board also took steps to make it harder for Simon to wrest control of the company.
To block an expected effort to place five Simon nominees on the Macerich board, the current directors created a temporary "classified board" structure, which sets terms and classes for each of the directors.
Macerich also created a share purchase-rights plan for shareholders which would force huge additional costs on Simon if it raises its shareholding in Macerich above 10 percent.
"After careful consideration, the Macerich Board of Directors unanimously determined that  Simon Property Group's unsolicited proposal significantly undervalues Macerich and fails to reflect the full value of our portfolio of unique and irreplaceable assets and our positive growth prospects," Arthur Coppola, Macerich chairman and chief executive, said in a statement.
Simon reported a 3.6 percent stake in Macerich in November and since then had sought in vain to engage the Macerich board in friendly merger talks.
The deal would combine the country's largest shopping center operator, with about 182 million square feet (17 million square meters) of leasable space in 109 properties, with the mid-sized Macerich, holding 55 million square feet in about 60 properties.
Simon owns the Premium Outlets and Mills chains of suburban malls. It also owns 18.3 percent of France's retail property power Klepierre. Macerich's mall  properties are mainly in California, Arizona and the New York region.