U.S. officials say the International Space Station may need to be temporarily evacuated unless Russia proceeds with the launching of its Soyuz rockets by November.

NASA space station program manager Mike Suffredini said the six astronauts aboard the ISS may have to leave the craft unless Russian scientists discover what caused last week's crash of an unmanned cargo ship that was headed to the facility.

On Monday, Russia postponed its next manned spacecraft mission to the ISS by at least a month after an unmanned ship using a similar rocket crashed into Siberia on August 24. The vessel was carrying three tons of supplies to the space station.

The ISS crew – three Russians, two Americans, and one Japanese – cannot stay in orbit for longer than six consecutive months because of the risk posed by exposure to radiation.

Three astronauts are scheduled to leave the space station next month; the other three are due to leave in mid-November.

Russian officials say, pending an investigation, they plan to test one or two unmanned Soyuz rockets in October before going ahead with the manned mission to the ISS by early November.

NASA officials say, if necessary, they could command the space station from the ground indefinitely. However, some scientific experiements would have to be suspended, and the danger of a malfunction leading to a loss of the ship is much greater.

While the crew has enough supplies to stay in orbit until next summer, the vessels designed to take them home will soon expire. The two Soyuz capsules, currently docked at the space station, are only certified to last for 200 days in orbit.

Russia's Soyuz spacecraft have been used to transport astronauts to and from the space station for two years. NASA formally ended its manned space shuttle missions just weeks ago.