U.S. space officials are concerned NASA will have to rely on other countries to carry astronauts into space after its three space shuttles are retired.

NASA plans to retire its aging space shuttles in 2010 because of their high cost and safety concerns, with nothing scheduled to replace them until at least 2015, The Washington Post reported. That means there will be no way to transport astronauts and cargo to the International Space Station without having to pay another country to do it.

Right now, Russia is the only country that can fly humans to the space station. "We will be largely dependent on the Russians, and that is a terrible place for the United States to be. I'm worried and many others are worried." NASA Administrator Michael Griffin told the newspaper.

NASA's current budget calls for spending $2.6 billion for transportation to the space station between fiscal 2009 and 2013.

Copyright 2008 by United Press International