The latest delay to the shuttle's launch was announced on Wednesday after Nasa discovered that one of the craft's ne of three cells providing electricity had malfunctioned.
Atlantis had been scheduled for launch from the Kennedy Space Centre, Florida, on Wednesday.
Atlantis' mission is to resume construction of the International Space Station, which was stopped after the destruction of shuttle Columbia in 2003.
Nasa said it would try to launch the shuttle on Friday but said that it might postpone the launch further.
"I still am hopeful and I certainly believe that there's an opportunity to launch Friday morning," Wayne Hale, the space shuttle program manager, said.
"We are going to set up for a launch Friday morning but we need to get satisfactory answers to some of our engineering questions."
"If we cannot prove that we are safe to fly then we won't fly."
Thursday and Friday are the last days for launch attempts before late October when lighting and other conditions will again be suitable for a flight to the space station.
Nasa had planned to launch Atlantis and its six-member crew last week, but a lightning strike and a storm triggered a series of postponements.
The mission has already been delayed more than three years while Nasa recovered from the 2003 Columbia disaster, when seven astronauts died after the shuttle exploded on re-entry.