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.
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 USD 70 million per seat.
The Wall Street Journal cited unnamed industry sources as saying Boeing was considered a favorite in the NASA bids.
