Silverstein Properties, the developer of the $11.7 billion World Trade Center project, is having a tough time baiting tenants for the 3 World Trade Center building, the third-tallest in the complex. This is bad news for the Richard Rogers design, which the Pritzker Prize-winning architect intended to rise 1,170 feet above the ground.

According to a “pre-lease” agreement Silverstein entered with the Port Authority of New York and New Jersey, the city required that Silverstein secure enough tenants to fill at least 400,000 square feet of the planned 2.8 million-square-foot building, as well as obtain $300 million of private equity and private construction financing. If these caveats aren’t met — and thus far, they haven't been — the city will withdraw its financial support, and construction would stop where it currently is at a meager seven stories, 73 short of the Rogers's plans.

Attracting tenants in the current economic climate is foreseeably a hard sell, but owner Larry Silverstein remains “optimistic,” as he said in a written statement Monday. He claimed to be speaking with a number of potential clients, and there is good news: the podium that would cap the seventh floor won't be completed until next year, buying him some time to work his spiel. Even if he doesn’t finalize any deals in time, the podium would be built with the option of building on top of it in the future.

Nearby, 2 World Trade Center is facing the same dilemma. The planned 88-story tower only reaches the ground level, as a lack of tenants slowed construction shortly after the completion of its underground portion, according to the Associated Press. Disputes between the Port Authority and the National September 11 Memorial & Museum have halted construction of the new institution. At least Silverstein's 1 World Trade Center has a bit of luck —  it's 60 percent leased and still planned to open as scheduled at the end of 2013. What its tony tenants will be looking out at from its windows remains to be seen.