The battle for General Growth Properties Inc., owner of more than 200 U.S. malls from Boston to Hawaii, is turning into the biggest real estate fight since the sale of Sam Zell's Equity Office Properties Trust.

Westfield Group, a Sydney-based property investor with stakes in 55 U.S. retail centers, signed an agreement letting it assess General Growth's finances, a person familiar with the pact said. That could put Westfield in position to vie for the bankrupt company's assets as part of a contest already embroiling Simon Property Group Inc. and Brookfield Asset Management Inc.

“;For many years the investing community failed to understand the real value of high-quality regional malls,”; said Rich Moore, managing director at RBC Capital Markets in Solon, Ohio. “;We've just gone through the worst recession in our history, and these things are largely unscathed.”;

Commercial real estate deals in the U.S. dropped to $44 billion last year, down 67 percent from 2008 and the lowest in records going back to 2001, according to New York-based property research company Real Capital Analytics Inc. Globally, retail real estate transactions totaled $50 billion, down 40 percent from a year earlier.

Plunging commercial real estate values—down 41 percent since their 2007 peak—have made landlords reluctant to sell.

The last time such a high-profile portfolio came to the market was in 2006. Blackstone Group LP beat out Steven Roth's Vornado Realty Trust to buy Zell's Equity Office, then the largest U.S. office landlord, for $39 billion.

General Growth, which owns Ala Moana Center and Ward Centers, and Brookfield unveiled a plan Wednesday that calls for the Toronto-based company to invest $2.63 billion in the mall owner and take a 30 percent stake.

Simon, which bid $10 billion for its biggest rival, called the Brookfield plan a “;complex piece of financial engineering that is so highly conditional as to be illusory.”;

The target of the fight owns some of the most valuable properties in retail real estate. General Growth, the second-biggest U.S. mall owner, has four of the five U.S. malls with the highest sales per square foot. Simon owns the best performer, according to 2009 estimates by real estate research company Green Street Advisors in Newport Beach, Calif.

General Growth's best-performing malls are the Grand Canal Shoppes and Fashion Show in Las Vegas, Ala Moana Center and Whalers Village in Lahaina, according to Green Street. All four have annual sales per square foot of $1,100 to $1,200.

General Growth announced plans Wednesday to split itself into two companies as part of an effort to exit bankruptcy with Brookfield's investment.

The proposal would give General Growth equity holders total consideration of $15 a share, the company said. General Growth stockholders would receive one new General Growth share with an initial value of $10, plus one share of a new company, to be called General Growth Opportunities, with an initial value of $5, for each share they own. Unsecured creditors would be repaid in full plus interest.

Under the unsolicited offer by Simon, equity investors would have received about $9 a share and unsecured creditors paid in full for about $7 billion. General Growth said at the time the offer was too low and that it would invite other bids.