The prime minister and deputy prime minister of Luxembourg were in Florida for the launch, along with the prince and princess of Luxembourg, SpaceX said.

"There you saw a successful liftoff of the Falcon 9," a SpaceX commentator said as the rocket launched on a sunny day from Cape Canaveral at 4:25 pm (2125 GMT).

The satellite will enable "secure communication links between theaters of tactical operations, for maritime missions or over areas affected by humanitarian crises," said a SpaceX statement.

GovSat-1 is bound for a distant, geostationary orbit and will support communications within Europe, the Middle East and Africa.

It will also enable operations over the Atlantic and Indian oceans and the Mediterranean and Baltic seas.

SpaceX did not attempt to land the first stage of the rocket after launch. The launch did however use a booster that flew last year.

The California-based company headed by space and solar energy tycoon Elon Musk has landed 21 rockets after launch as part of its effort to re-use costly rocket parts and bring down the costs of spaceflight.

Wednesday's launch comes three weeks after SpaceX blasted off a secretive US government payload, called Zuma.

According to media reports, the satellite did not make it into orbit, though the Pentagon refused to elaborate on what happened.

SpaceX said everything functioned fine with the rocket, and declined to comment further, citing national security concerns.