The grounded shuttle fleet will increase the cost of completing the International Space Station and could expose the outpost's two-man crew to more risk than originally was expected, according to a General Accounting Office report released Tuesday.

Neither NASA nor the GAO could accurately estimate what the cost of the shuttle delays could be, according to the report.

The lack of shuttles to ferry heavy items to the station also hampers NASA's ability to correct known safety concerns, Local 6 News partner Florida Today reported.

With only two crew members currently on board, the station is in "survival mode" until the shuttle fleet is cleared to fly again, the report's author Allen Li wrote.

"We've reported many times on how the cost of the station is going up," said Allen Li, the report's author. "Now we're talking about a situation where there are now additional factors that are going to impact the final cost."

For example, added shielding to protect the crew from orbital debris is on hold, according to the report. NASA estimates the probability of space debris penetrating the crew's living quarters increases by 1.6 percent each year the new shielding is not installed.

Since 1985, Congress has appropriated $32 billion for the station, which originally was estimated to cost about $10 billion.

In 2001, the Bush administration canceled several of the station's planned modules to offset more than $4 billion in cost overruns.

Space agency officials reviewed the GAO report and agreed with its findings.