The next shuttle mission had been scheduled for September, but now is expected to occur no earlier than March.
The move comes as seven members of a larger oversight panel issued a scathing critique of the shuttle program Wednesday.
Some of the same "disturbing" traits that contributed to the Columbia tragedy were still present in the months leading up to the shuttle Discovery's liftoff, the members said.
"We expected that NASA leadership would set high standards for post-Columbia work," the panel members wrote. "We were, overall, disappointed."
The minority report said poor leadership made the shuttle's return to space on July 26 more complicated, expensive and prolonged than it needed to be. So much emphasis was placed on trying to meet unrealistic launch dates that some safety improvements were skipped, said the group.
"Another disturbing trait that we observed was that personalities were allowed to dominate over strict process," the seven panel members added.
The critics include a former shuttle astronaut, former undersecretary of the Navy, former Congressional Budget Office director, former moon rocket engineer, retired nuclear engineer and two university professors.
"NASA needs to learn the lessons of its past ... lessons provided at the cost of the lives of seventeen astronauts," they said, referring to the seven killed aboard Columbia and 10 others who died in the Challenger and Apollo 1 accidents years earlier.
The seven critics are part of the 26-member task force that monitored NASA's progress in meeting the recommendations set forth by the Columbia accident investigators. The entire task force concluded in late June in an advance summary — just a month before Discovery's liftoff on the first mission since the Columbia disaster — that the space agency failed to satisfy three of the 15 return-to-flight recommendations.
Those three failed recommendations were arguably the most critical: an inability to prevent dangerous pieces of foam and ice from breaking off the fuel tank during launch; an inability to fix any damage to the shuttle in orbit; and a failure to make the shuttle less vulnerable to debris strikes.
As it turned out, a large, potentially deadly chunk of foam insulation broke off Discovery's modified fuel tank during liftoff. Unlike in Columbia's tragic case, the piece did not hit Discovery. Nevertheless, NASA grounded its shuttle fleet.
The next shuttle mission now is expected to occur no earlier than March.
The co-chairmen of the task force, retired Apollo astronaut Thomas Stafford and retired shuttle astronaut Richard Covey, refused to comment Wednesday on the observations of individual panel members.