MOSCOW, December 31 (RIA Novosti) - Space Adventures, a U.S.-based company that organizes private space flights under an arrangement with Russia's space agency, has published a price list for "space services" on its website.

"Today, for the first time, Space Adventures offers spaceflight participants the unique opportunity to walk in space" at $45-55 million a go, the company said.

The first spacewalk was performed by cosmonaut Alexei Leonov in March of 1965.

The price of a "ticket" on a 10-day scheduled mission to the International Space Station (ISS) has risen from $30 million to $35-45 million.

The company said that every six months Russia's space agency, Roscosmos, launches a new Soyuz spacecraft and crew to the ISS. These missions are commonly referred to as "taxi missions" because they are used to rotate the long-duration crew on the station, as well as, swap out the Soyuz spacecraft that has been docked at the station for the preceding six months.

Founded in 1998, Space Adventures bills its mission as opening spaceflight and the space frontier to private individuals, to "facilitate the creation of new vehicles and markets that will open up the resources of space for human benefit." It is the only company able to offer space tourism with national space programs.