(CNN) -- The launch of the space shuttle Endeavour, originally scheduled for April 29, has been delayed again, NASA said Friday.
The next launch attempt will be "no earlier than May 16," said NASA spokesman Allard Beutel. If the shuttle launches on that day, liftoff would be at 8:56 a.m. EDT.
NASA had previously said that the final flight for the Endeavour wouldn't be any earlier than May 10, while sources had told CNN the next liftoff could be as late as May 13.
Technicians this weekend will continue to repair and retest the electrical system to determine what caused a circuit to short out, causing the cancellation of Endeavour's April 29 launch, officials said.
NASA repair crews have already replaced a distribution box that shorted out a circuit supplying power to heaters for the orbiter's hydraulics system.
"They're getting close," Beutel said.
The scrubbed April 29 launch postponed what promised to be an emotional moment for the shuttle's commander, Mark Kelly.
Kelly's wife, U.S. Rep. Gabrielle Giffords, D-Arizona, traveled to Florida hoping to watch the shuttle's ascent. Giffords was shot in the head during a January 8 assassination attempt at a public event in Tucson, Arizona. She has been recovering at a Houston rehabilitation hospital.
Giffords returned Sunday to the TIRR Memorial Hermann center in Houston, according to a post on her Facebook page. She is expected to attend the next launch attempt.
NASA management is scheduled Monday to brief the news media from the Kennedy Space Center in Florida on the progress of repairs.