NASA said Monday that it had reached an agreement with United Launch Alliance (ULA) to try to adopt the Atlas V commercial rocket to send astronauts to the International Space Station (ISS).

This NASA TV video grab shows the Atlas V rocket as it takes off in 2010.

ULA is a joint venture between Boeing and Lockheed Martin designed to provide cost-efficient rockets to send US government missions into space.

The agreement was unveiled as the shuttle Atlantis prepares to return to earth Thursday from the ISS, its final voyage after three decades of space shuttle flights.

It will be at least four years until the United States will be able to transport its astronauts to the ISS on anything other than Russian Soyez spaceships.

Having ULA on board may speed the development of a commercial crew transportation system for the International Space Station, allowing NASA to concentrate its resources on exploring beyond low Earth orbit," said NASA administrator Charles Bolden in a statement.

Under the agreement, NASA and ULA will jointly try to figure out the best way to use the Atlas V rocket to launch an astronaut into space.

Several companies competing to partner with NASA to build a successor to the space shuttle -- like Sierra Nevada Corp. and Blue Origin -- have already chosen the Atlas V to launch future commercial payloads.

Others, like Boeing, are seriously considering this option, while companies like SpaceX are developing their own rocket.

"We believe this effort will demonstrate to NASA that our systems are fully compliant with NASA requirements for human spaceflight," said George Sowers, ULA\'s vice president of business development. "ULA looks forward to continued work with NASA to develop a US commercial crew space transportation capability providing safe, reliable, and cost effective access to and return from low Earth orbit and the International Space Station."

Since it went into service in 2002, the Atlas 5 rocket family has mostly provided missions for the US Defense Department. It\'s been involved in 26 launches with a 100 percent mission success rate.