Planners say an 80-story skyscraper under construction at ground zero may have to stop at seven stories unless the developer can line up more tenants.

Silverstein Properties said Monday it is still looking for tenants to fill the first 10 floors of Three World Trade Center.

The Port Authority of New York and New Jersey will not guarantee the financing that Silverstein needs to finish the building unless it gets those leases.

Construction would end at the so-called "podium" level on the seventh floor. The floors below would be filed mainly with retail stores.

Both Silverstein and the Port Authority say they are confident the developer can get enough tenants lined up. But many companies in New York are reluctant to invest in new offices because of the economy.

(Copyright 2012 by The Associated Press.  All Rights Reserved.)