A SpaceX Falcon 9 rocket blasted off from Florida on a Nasa cargo run to the International Space Station on Friday, and its reusable main-stage booster landed on an ocean platform minutes later in a dramatic spaceflight first.

The successful autonomous touchdown of the booster at sea marked another milestone for billionaire entrepreneur Elon Musk and his privately owned Space Exploration Technologies in the quest to develop a cheap, reusable rocket, expanding his edge in the burgeoning commercial space launch industry.

The liftoff at 4:43 p.m. EDT (2043 GMT) from Cape Canaveral Air Station also marked the resumption of resupply flights by SpaceX for NASA following a launch accident in June 2015 that destroyed an earlier cargo payload for the space station.

About 2-1/2 minutes after Friday's launch, the main part of the 23-story tall, two-stage SpaceX rocket separated, turned around and headed toward a landing platform floating in the Atlantic about 300 km northeast of Cape Canaveral.

A live video feed broadcast on NASA television showed the rocket booster, its four landing legs extended, descending over the ocean before settling itself upright on the barge-like platform, roughly eight minutes after launch.

"The rocket landed instead of putting a hole in the ship or tipping over," Musk told reporters at the Kennedy Space Center a short time later. "We're real excited about that."

Four previous at-sea landing attempts had failed. But a Falcon 9 main-stage rocket achieved a successful ground-based touchdown in December, the first ever during an actual commercial space mission.

President Obama hailed the latest accomplishment on Twitter, saying, "Congrats SpaceX on landing a rocket at sea. It's because of innovators like you & NASA that America continues to lead in space exploration."

The reusable rocket booster should arrive back in Florida on Sunday and will be test-fired about 10 times, then likely re-launched, probably on a commercial flight, as early as May, Musk said.

SpaceX plans to start launching rockets about every two weeks from its sites in Florida and California later this year as the company tackles satellite-delivery orders worth some $10 billion, company officials said.

Roughly half the upcoming missions will leave the Falcon 9's booster with too little reserve fuel to fly all the way back to the launch site for a return landing, so the ability to land at sea is essential, Musk said.

He estimates each Falcon 9 booster should be good for 10 to 20 launches, possibly up to 100 with minor refurbishment.

SpaceX also plans to debut a heavy-lift version of the Falcon rocket this year, equipped with 27 engines powering its first-stage, compared to the nine currently used.

The cargo ship that lifted off on Friday, a capsule dubbed Dragon, was due to arrive on Sunday at the space station, the $100 billion laboratory flying about 400 km above Earth. It is packed with about 3,175 kg of food, supplies and experiments, including a prototype inflatable habitat.

Built by Nevada-based Bigelow Aerospace, the lightweight fabric habitat will be tested to see how it compares with more traditional orbiting enclosures made from metal in the hostile environment of space.

The US space agency is interested in expandable habitats to serve as crew living quarters during eventual three-year trips to and from Mars.-Reuters