The Delta IV heavy-lift launch vehicle has been launched into orbit with the secret NROL-44 satellite of the US National Reconnaissance Office (NRO), the United Launch Alliance (ULA) operator said.

The launch of the three-stage rocket was carried out on Thursday from the SLC-37B launch complex in Florida, Interfax reports.

ULA is a joint venture between Boeing and Lockheed Martin to carry out launches for the Pentagon and the US intelligence community.

The launch of the reconnaissance satellite, which was planned to be carried out back in June, was postponed several times due to technical problems and bad weather.

The purpose, orbit, size and other characteristics of the secret American satellite NROL-44 have not been officially reported.  The mission and capabilities of this type of satellites are strictly classified.

Since 1995, seven such satellites, developed by the NRO with the participation of the CIA, have already been launched into geostationary orbit.