Updated

NASA says it still has confidence in the quality of Russia's manned rockets, despite an embarrassing series of glitches and failures in the Russian space program.

A leak developed recently during a test of the next Soyuz capsule scheduled to launch astronauts to the International Space Station, so Russian space officials have decided not to use it. That delays upcoming launches.

NASA relies solely on Russia to take crews to the space station.

NASA space station manager Michael Suffredini said he still considers the Soyuz rocket the world's most reliable space system.

"I have confidence in the focus and abilities of the managers who build the systems and fly those systems," Suffredini said Thursday during a NASA teleconference.

The Soyuz leak means that the six crew members at the space station will now spend a few extra weeks in space. American Dan Burbank, who is the station commander, and Russians Anton Shkaplerov and Anatoly Ivanishin will stay in orbit until the end of April. American Don Petit, Dutch astronaut Andre Kuipers and Russian Oleg Konenko, will stay in space through the end of June for about 193 days in space, pushing close to the limit of 200 days that NASA likes.

The latest problem comes after a series of failures in unmanned Russian rockets that raised questions about quality control in the nation that launched the first satellite and human into space. Last month, a spacecraft that was supposed to go to a Mars moon crashed back to Earth after a launch failure. And in the past six months, a Russian communications satellite and a cargo ship to the space station have crashed.

"They've had a pretty challenging year that's true," Suffredini said. But he said that doesn't really have anything to do with the workhorse manned Soyuz capsule.

A private U.S. rocket — the Dragon built and operated by Space Exploration Technologies — probably won't launch until early April on a first-ever commercial resupply of the space station, Suffredini said. It had been set for a launch this month, but was already delayed.

SpaceX spokeswoman Kirstin Brost Grantham said the company "will not launch before late March." A date should be set in about two weeks.

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Online:

NASA: www.nasa.gov

Space Exploration Technologies: http://www.spacex.com/index.php