WASHINGTON - NASA has delayed the launch of its Lunar Reconnaissance Orbiter (LRO) aboard a United Launch Alliance Atlas 5 rocket from late this year until the end of February at the earliest to make way for a military payload slated to fly atop a similar vehicle.

"Because of high demand for Atlas 5 launches for the next 12 months, NASA has agreed to a request to exchange launch dates with another mission, allowing that mission to launch earlier," NASA spokeswoman Nancy Jones told Space News. "The new LRO launch window now opens on the 27th of February 2009, and continues through the end of March."

Jones did not say who had asked to swap launch dates with LRO. Another NASA official said the request was made by the U.S. Defense Department, which wants to have its payload on orbit before the end of this year.

The Florida newspaper Florida Today reported that the military payload would be a space plane prototype built for the Pentagon. ?

The LRO had been on schedule for a late 2008 liftoff from Cape Canaveral, Fla. The mission development team at NASA's Goddard Spaceflight Center in Greenbelt, Md., will use the additional time for more risk-reduction testing and to address any problems the spacecraft might encounter during environmental testing currently under way, Jones said.

NASA officials have been warning for months that a combination of zero schedule slack and a busy end of the year at Cape Canaveral could push the LRO's launch into 2009.

Florida Today contributed to this report.