The U.S. space agency, NASA, says it is not certain when it will launch the space shuttle Discovery.
NASA officials said Friday that they are no closer to solving a fuel sensor problem that canceled Wednesday's planned lift-off.
Deputy Shuttle Program Manager Wayne Hale said NASA will not schedule a new launch until at least four days after the problem is fixed.
New safety rules require that shuttle launches take place during daylight. NASA also must factor in the mission's planned rendezvous with the International Space Station.
Mr. Hale said NASA may extend its July launch window a few days into August. If the problem persists, the agency would be forced to launch the shuttle in September.
The Discovery mission will be the first shuttle flight since the Columbia disaster in 2003.
Some information for this story provided by AP.