Officials said the shuttle Atlantis can be launched to stage a rescue if needed, but that three more days are required to finish the damage assessments.

"There is some concern it might have struck the wing," the shuttle deputy program manager Wayne Hale said of one of the rogue shards of foam.

Officials showed digital images of where the pieces of foam came off during Tuesday's launch and of "possible coating damage" and other "scuffs" that might have occurred to the shuttle.

However, Hale told reporters there was a "divergence of opinion" among NASA analysts of whether the foam had actually struck the wing.

Steve Poulos, manager of the orbiter project office, said:"We are very confident that we are going to have a very clean vehicle that is going to be ready to re-enter."

"There are 11 indications of potential impacts," Poulos said, adding: "We might have four areas on the wing leading edge where there might have been an impact."

He said a full assessment of the images taken and more inspections to be carried out by the crew would take three more days.

Asked about rescue planes, following NASA's decision to suspend future flights, Hale said "we are holding Atlantis on readiness" for a rescue but stressed that "we are nowhere near doing that."

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