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The launch of the space shuttle Discovery has been delayed and may be scrubbed because of cracks found in a high-speed turbopump of the spacecraft's counterpart, Atlantis.

NASA engineers said Wednesday that the delay of the Discovery flight until at least mid-March could force a postponement in a scheduled April launch of Atlantis. But the Atlantis flight has priority and could force the cancellation of the Discovery launch, space agency officials said.The National Aeronautics and Space Administration made the announcement after shuttle managers reviewed an engineering analysis of cracks discovered in one of Atlantis' high-speed turbopumps after a December flight. Failure of the pumps could cause an explosion that could kill the crew.

Officials said Discovery will be moved to the launch pad early Friday and three suspect pumps are to be replaced in conjunction with other launch preparations.

Because of the uncertainty of the availability of new pumps and the length of time to make the replacements, NASA said it would not set a firm launch date until a flight readiness review in late February.

The agency had been aiming for a Feb. 23 liftoff for Discovery, but a series of technical delays not related to the pumps already had delayed that date several days.

If the date slips past March 18, the planned April 28 launch of Atlantis will have to be delayed, officials said.

Officials have said the Atlantis mission in April has priority because Atlantis will be carrying the Venus-Magellan probe and will have only a 25-day "window" to launch it.

Discovery is to carry a communications satellite. NASA officials had said previously that its flight would be put off until later in the year if it couldn't get off the ground by about March 15.

NASA said it could delay the Atlantis flight a few days, although it would prefer not to do so. Officials would like to preserve the entire launch window in case of problems.

Only one shuttle launch pad is currently available. A second is being refurbished.

Questions were raised about the three turbopumps when engineers found two tiny cracks in a bearing unit in one of Atlantis' pumps after it completed the second post-Challenger mission in December.

They believe the cracks were caused by stress corrosion resulting from moisture trapped inside the bearing housing during the manufacturing process.