The next space shuttle launch will probably be delayed at least until March to give NASA more time to make engineering changes aimed at reducing the craft's foam-shedding problem, agency officials said yesterday.

The delay will also give officials a chance to consider an independent report, commissioned by the agency and released Wednesday, that analyzed NASA's efforts to correct organizational failings that contributed to the loss of the shuttle Columbia in 2003.

That 220-page assessment, by a 26-person committee of experts, is mostly positive. But it includes a highly critical "minority report" signed by seven committee members who said the agency has continued to ignore certain risks to get the shuttle program aloft again.

"It appears to us that lessons that should have been learned have not been," the minority asserted, referring at one point to a "cycle of smugness substituting for knowledge."

Speaking to reporters at headquarters yesterday, NASA Administrator Michael D. Griffin said he had not had a chance to fully study the report, but he made clear he is not afraid to consider the criticisms. He said he had been approached by the committee's leaders toward the end of its deliberations and was told that some members had dissenting opinions and criticism. When the leaders asked him whether those opinions should be included in the report or distributed separately, Griffin recalled yesterday, he told them to include them.

"We welcome the advice . . . in the spirit of openness and honest acceptance," he said yesterday, adding that he made that decision without reading the comments ahead of time.

Griffin denied charges leveled by some critics that the agency is being overly driven by a face-saving desire to complete most of the international space station before the aging shuttle fleet is mothballed.

There has been a "change of thinking," Griffin said. "We are not trying to get a specific number of flights out of the shuttle system. We are working toward an expeditious but orderly retirement of the shuttle," he acknowledged. But at the same time, he said, "we believe that, absent major problems, we can essentially complete the space station in the time we have available."

Griffin and William H. Gerstenmaier, the agency's new director of manned space operations, said engineers are still analyzing data from the recent flight of Discovery, which lost one large piece of foam and several smaller ones. A similar shedding of foam caused Columbia's disintegration upon reentry 21/2 years ago.

NASA scientists have not determined why the foam flew off Discovery despite a multiyear effort to deal with the issue, and it will be two to three more weeks before the agency settles on a plan for design changes, Gerstenmaier said. Expectations are that the launch, initially slated for next month, will be scheduled for around March 4.

"Earlier opportunities don't make sense for us," Gerstenmaier said. "We still have a lot of work before we decide on a particular repair technique. We're going to let the data drive us."

A later launch date will also give NASA the fortuitous opportunity to switch the order of the shuttles to be launched, Gerstenmaier said. By preparing the recently returned Discovery for a launch in March, Atlantis -- the craft currently on deck -- can be reserved for the following flight, which is slated to carry a major component for the space station. Being lighter than Discovery, Atlantis is better able to carry such loads. And NASA would have been hard-pressed to fly Atlantis twice in quick succession, as would have been required to keep the station's construction on schedule.

Asked whether the delay until March reduces the odds that the shuttle program will find time to send a repair mission to the Hubble Space Telescope, Griffin said the impact would be primarily budgetary.

"The longer we go without committing . . . the more it costs" to go to Hubble, Griffin said, adding that after 2007, the mission's price will grow by about $10 million a month.

Meanwhile, the two crew members aboard the space station emerged yesterday in Russian spacesuits for a six-hour spacewalk.

Cosmonaut Sergei Krikalev and astronaut John Phillips floated out of the station just after 3 p.m. Eastern time. On their to-do list: replace several science experiments attached to the outside of the station, take photographs, install a new television camera and move a grappling arm to a new location.