If the space shuttles retire in 2010 as planned, NASA won't have an autonomous means of getting astronauts to the International Space Station until at least 2014. (Associated Press)

NASA is looking into extending its space shuttles past their planned 2010 withdrawal from service, according to an e-mail made public over the weekend.

The move comes as the U.S. space agency faces a dilemma.

If it retires the shuttles as originally scheduled, it won't have an autonomous means to get astronauts or cargo to the International Space Station, or ISS, until at least 2014, when its next generation of spacecraft, the Orion, is slated to enter service.

NASA would have to rely on Russia allowing U.S. astronauts and payloads to piggyback on its launches, or — the current stopgap plan — it could buy Russian spacecraft and launch them itself.

The frost that has chilled U.S.-Russian relations during recent events in Georgia has made both of those alternatives unpalatable. So NASA is launching a study to determine how it might extend shuttle service.

"We want to focus on helping bridge the gap of U.S. vehicles travelling to the ISS as efficiently as possible," wrote John Coggeshall, manager of manifest and schedules at Johnson Space Center in Houston, in the e-mail.

The missive describes NASA chief Michael Griffin's order for a study to find out whether the shuttle could fly until 2015.

Griffin has previously opposed extending the shuttle program, which first launched in 1981 with a 55-hour flight by Columbia, because the money and effort required to do so would hurt progress with the Orion.

The Orion craft, to be paired with Ares launch vehicles, are slated to fly to the moon by 2019 and to Mars in about 2037.

With files from the Associated Press