A Delta IV rocket carrying a secret payload for the National Reconnaissance Office (NRO) blasted off on Monday from Cape Canaveral, the launch company said on its website.
The launch took place at 1:58 am Moscow time [22:58 Sunday GMT]. The blastoff, initially scheduled for November 18, had been delayed several times.
Commercial launch company United Launch Services (ULA) said the mission was "in support of national defense," without giving any further details.
Fox News earlier said the payload, known only as NROL-32, is widely assumed to be "the largest satellite in the world," with a mission "to bolster U.S. eavesdropping abilities."
Delta IV is the biggest unmanned rocket currently in service in the United States.
MOSCOW, November 22 (RIA Novosti)