Nasa to Make Announcement on Manned US Spaceflights on Tuesday

The US space agency said Tuesday that a "major announcement" is coming at 8pm GMT regarding the return of human spaceflight launches to the United States.

Nasa, which has been unable to send people to space since the retirement of the space shuttle in 2011, said the announcement would be made at a news conference from Kennedy Space Center in Florida, and would be broadcast live on Nasa's television station and website.

"We're returning human spaceflight launches to America. Learn who will take crews to the ISS (International Space Station)," Nasa said on Twitter.

A Nasa spokesman declined to give further details until the announcement, which is timed to coincide with the closing of the US markets.

The agency has spent hundreds of millions to help private companies like SpaceX, Boeing and Sierra Nevada develop their own crew transport vehicles so that Americans could launch flights to the ISS by 2017.

In the meantime, the world's astronauts have had to rely on Russia's Soyuz spaceships for transport to the orbiting outpost at a cost of $70 million per seat.

The Wall Street Journal cited unnamed industry sources as saying Boeing was considered a favorite in the Nasa bids.