Training of the crew for the first entirely private trip to the International Space Station (ISS) is to begin soon, Axiom Space, the company behind the flight, said Monday at a joint press conference with NASA.

Four astronauts are to be launched to the ISS in late January aboard a rocket built by another space company, Elon Musk's SpaceX.

Only one of the four -- NASA veteran Michael Lopez-Alegria -- has been in space before.

The other three are businessmen -- Larry Conner, an American, Mark Pathy, a Canadian, and Eytan Stibbe, an Israeli.

The mission dubbed Ax-1 is to last around 10 days, said Axiom Space president and CEO Michael Suffredini.

The astronauts will work and live in the American section of the space station and plan to conduct a number of scientific experiments while in orbit.

"We'll be starting what I would call serious training next week," said Lopez-Alegria, the Ax-1 commander.

"From there the pace will pick up, and we'll all be immersed essentially full time in ISS systems and Crew Dragon training starting in the fall."

He said the four men had only been together a "handful of times" because of the Covid-19 pandemic but would take a "bonding" camping trip in Alaska in July.

Lopez-Alegria said he will start full-time training in August and Connor, the mission pilot, will begin in September.

The International Space Station photographed in 2018 from a Soyuz spacecraft
The International Space Station photographed in 2018 from a Soyuz spacecraft NASA / HO

Starting in October, all four will begin Houston-based training on the ISS systems and SpaceX's Crew Dragon capsule.

Axiom Space considers the mission a first step in its plan to build the first commercial space station.

Asked about the cost of Ax-1, Suffredini said we "generally don't talk about specific pricing."

"It's been widely reported -- numbers in the tens of millions -- which I wouldn't argue with," he said.

Phil McAlister, director of NASA's commercial spaceflight development, said the mission is a "renaissance in US human spaceflight."

"This is a real inflection point," he said.

The US space agency is aiming for two such private missions a year.

"We are seeing a lot of interest in private astronaut missions," said Angela Hart, NASA's manager of commercial low-Earth orbit development.

"At this point the demand exceeds what we actually believe the opportunities on station will be," Hart said.

Seven "space tourists" flew to the ISS between 2001 and 2009 aboard Russian Soyuz rockets.