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SpaceX says it has resolved the problem that held up liftoff of an unmanned Dragon cargo ship to the International Space Station — and is shooting for another launch attempt on Friday.

NASA confirmed the launch date on Wednesday, two days after a last-minute leak on SpaceX's Falcon 9 rocket delayed the mission. Stormy weather, however, is forecast for launch time at 3:25 p.m. ET Friday. Saturday is the backup launch date.

Because of the shifting scenarios for SpaceX's launch, Mission Control has rescheduled a spacewalk to replace backup computer that failed late last week. The prime computer has been working fine, but NASA wants to get a new backup installed outside the station as soon as possible. These computers control the pointing of the radiators and solar wings, among other things.

SpaceX's Falcon 9 rocket is now due to send a Dragon cargo capsule to the International Space Station on Friday, weather permitting. Saturday is the backup launch date.

NASA astronauts Rick Mastracchio and Steven Swanson had been preparing for a Tuesday spacewalk, but now the outing will take place either on Easter Sunday or next Wednesday, depending on when — or if — the cargo ship flies. The Dragon contains more than 2 tons of supplies, including material that would prove useful for the repair but is not essential.

SpaceX said Monday's helium leak was caused by a bad valve in the system used to separate the rocket's first stage. Although a backup valve was working properly and could have supported the flight, SpaceX followed its own policy of canceling a launch in the event of equipment problems such as this.

The faulty valve is being replaced, the private company said in a statement, and inspections are under way to see if anything else might be wrong.

SpaceX and another commercial venture, Orbital Sciences Corp., resupply the space station under NASA contracts that have a combined value of $3.5 billion. If SpaceX isn't flying by Saturday, then Orbital Sciences will move to the front of the launch line, with a shipment in early May, officials said. That would push the Dragon launch into June.

— The Associated Press