NASA postpones debut test flight of next-generation moon mega-rocket

NASA on Monday postponed for at least four days the launch of its colossal next-generation rocketship on a long-awaited debut test flight, a planned six-week uncrewed voyage around the moon and back 50 years after Apollo's last lunar mission.

The countdown clock was halted about 40 minutes before the targeted launch time of 8:33 am EDT (1233 GMT), as the 32-storey-tall, two-stage Space Launch System (SLS) rocket and its Orion crew capsule awaited liftoff from the Kennedy Space Center in Cape Canaveral, Florida, reports Reuters.

The US space agency cited a problem detected on one of the rocket's main engines, after launch teams had begun filling the rocket's core fuel tanks with super-cooled liquid oxygen and hydrogen propellants.

NASA did not give a new launch date but said its first available backup launch opportunity was set for Friday, Sept 2.