NASA on Friday delayed space shuttle Endeavor's launch to no earlier than Monday afternoon due to technical problems with heaters in the shuttle's auxiliary power unit.

Space shuttle Endeavour sits on the launch pad at the Kennedy Space Center at Cape Canaveral, Florida, April 28, 2011. The Endeavor is scheduled for a Friday afternoon launch. [Xinhua/Reuters Photo]

"Shuttle Endeavor's launch now no earlier than Monday at 2:33 p. m. EDT (1833 GMT)," NASA said. "Engineers need that time to troubleshoot an issue that resulted in today's launch scrub."

During Friday's countdown, engineers detected a failure in one of two heater circuits associated with Auxiliary Power Unit (APU) 1. Heaters are required to keep the APUs' hydrazine from freezing on orbit.

U.S. President Barack Obama, touring storm damage in Alabama on Friday, had been expected to attend the planned 3:47 p.m. (1947 GMT) launch. Obama will still visit Cape Canaveral and then travel to Miami, where he is scheduled to speak at a community college commencement.

Endeavor's 14-day mission will deliver the Alpha Magnetic Spectrometer-2 (AMS) to the International Space Station. AMS, a particle physics detector, is designed to search for various types of unusual matter by measuring cosmic rays.

Its experiments are designed to help researchers study the formation of the universe and search for evidence of dark matter, strange matter and antimatter. Endeavor also will fly the a platform that carries spare parts that will sustain space station operations once the shuttles are retired from service.

The mission will feature four spacewalks to do maintenance work and install new components. These are the last scheduled spacewalks by shuttle crew members.

Endeavor, which has been promised to the California Science Center in Los Angeles upon its return, was the replacement ship for Challenger, which was lost in a 1986 explosion as it ascended over the Atlantic that killed seven astronauts.

It will be the second of NASA's three surviving shuttles to be retired. Sister ship Discovery, which will be transferred to the Smithsonian National Air and Space Museum, completed its last flight in March.

Atlantis' final launch is scheduled for June 28. When the U.S. space shuttle program officially ends later this year, the Russian space program's Soyuz capsule will be the only method for transporting astronauts to and from the station.