NASA will likely delay by as much as a month some space shuttle launches scheduled for next year because of a backlog in processing the shuttles' external fuel tanks, an agency spokesman said Monday.

If approved, the revised schedule would push back the first launch of 2007 to March 16 from Feb. 22; the launch of space shuttle Endeavour to June 28 from June 11; and the launch of Atlantis to Sept. 7 from Aug. 9.

Two other flights carrying international space station parts constructed by the European and Japanese space agencies still are scheduled for later in 2007.

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In the three years since the Columbia disaster, NASA's efforts to get the external fuel tanks ready for launch have been confounded by design changes and Hurricane Katrina, which damaged the tank assembly plant in New Orleans last year.

"The effects of Katrina are still being felt somewhat," NASA spokesman Kyle Herring said. "Getting back on track with the tank is obviously the biggest challenge there."

NASA is still putting a new fuel tank design through wind-tunnel tests, but the initial results have been promising.

Engineers hope the new design reduces the amount of insulating foam that drops off during liftoff from wedge-shaped brackets on the tank that hold pressurization lines in place. The first tank with the design change could be used during Atlantis' flight next March.

Foam that fell from space shuttle Columbia's fuel tank caused a gash in a wing in 2003, causing the spacecraft to disintegrate during re-entry and killing seven astronauts.

The next launch this year — the first at night in four years — is set for no earlier than Dec. 7. Space shuttle Discovery will deliver a crew member to the space station and allow astronauts to hook up power to solar wings that were installed on the space station last month.