SpaceX said it will fly two people to the moon next year, a feat not attempted since NASA's Apollo heyday close to half a century ago.

Tech billionaire Elon Musk — the company's founder — announced the surprising news.

Two people who know one another approached the company about sending them on a weeklong flight just beyond the moon, according to Musk. He won't identify the pair or the price tag. They've already paid a "significant" deposit, he noted.

Mr Musk said SpaceX is on track to launch astronauts to the International Space Station for NASA in mid-2018. This moon mission would follow about six months later, by the end of the year under the current schedule, using a Dragon crew capsule and a Falcon heavy rocket.

The moon mission is designed to be autonomous — unless something goes wrong, Mr Musk said.

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"I think they are entering this with their eyes open, knowing that there is some risk here," Mr Musk told reporters in a telephone news conference, a day after teasing via Twitter that an announcement of some sort was forthcoming.

"They're certainly not naive, and we'll do everything we can to minimise that risk, but it's not zero. But they're coming into this with their eyes open," said Mr Musk, adding that the pair will receive "extensive" training before the flight.

Mr Musk said he does not have permission to release the passengers' names, and he was hesitant to even say if they were men, women or even pilots. He would only admit, "It's nobody from Hollywood."

The passengers would make a long loop around the moon, skimming the lunar surface and then going well beyond, perhaps 300,000 or 400,000 miles distance altogether. The mission won't involve a lunar landing, according to Mr Musk.

It's about 240,000 miles to the moon alone, one way.

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NASA will have first dibs on a similar mission if it so chooses, Mr Musk said. The space agency learned of his plan at the same time as reporters, and was busy preparing a statement following the announcement.

"This should be a really exciting mission that hopefully gets the world really excited about sending people into deep space again," he said.

The crew Dragon capsule has not yet flown in space. Neither has a Falcon Heavy rocket, which is essentially a Falcon 9 rocket with two strap-on boosters, according to Mr Musk. He said there will be ample time to test both the spacecraft and the rocket, before the moon mission.

Mr Musk expects to have more moon-mission customers as time goes by.

Just late last week, NASA announced it was studying the possibility of adding crew to the test flight of its megarocket, at the request of the Trump administration. Such a flight to the lunar neighborhood wouldn't happen before 2019 at best — if, indeed, that option is even implemented.

Mr Musk said anything that advances the space exploration cause is good, no matter who goes first.

"This should be incredibly exciting," he said.

SpaceX is also working on a so-called Red Dragon, meant to fly to Mars around 2020 with experiments, but no people — and actually land.