Simon Property Group Inc. offered to buy General Growth Properties Inc. for about $10 billion as the world's largest shopping-mall operator seeks to absorb the No. 2 mall owner in the U.S. as it grapples with bankruptcy.

Although shopping-mall real-estate investment trusts have been struggling with declines in consumer spending, Simon is viewed as one of the healthiest. It reported better-than-expected quarterly results last month, and although Simon's business was still hurt by write-downs and lower occupancy rates, it predicted brighter days for 2010.

Meanwhile, Simon raised several billion dollars in the latter part of 2009 looking for opportunities to take advantage of woes in the commercial real-estate sector. Simon had said earlier this month it wasn't in active negotiations with General Growth.

The Chicago-based owner of 200 U.S. malls, filed for Chapter 11 bankruptcy protection in April, taking 166 of its malls into the case with it. Since then, it has restructured and extended the due dates of $11.6 billion in mortgages on its malls. But it still needs to reach similar deals with holders of another $3 billion of mortgages and to pay its $7 billion of unsecured debt with either cash or equity.