Hawthorne rocket maker SpaceX and Chicago aerospace giant Boeing Co. will share a contract to ferry U.S. astronauts to and from the International Space Station, NASA Administrator Charles Bolden announced today.

The contract for NASA’s Commercial Crew Program is worth up to $6.8 billion, Bolden said. Of that, $4.2 billion will go to Boeing. The initial contract is expected to cover the work necessary for both firms to certify spacecraft for manned NASA missions.

The agency’s objective is for SpaceX and Boeing Co. to be ready to launch astronauts into space by 2017. NASA’s chief said the agency’s planned reliance on private contractors for manned missions to the space station will allow the United States to forego assistance from Russia for launches, while developing a heavy lift rocket and planned Orion space capsule for manned missions to Mars.

NASA plans to use an updated version of SpaceX’s Dragon capsule for manned missions. The Dragon became the first private spacecraft to deliver cargo to the International Space Station and return to earth in October 2012. The space agency also plans to use Boeing’s CST-100 space capsule, which was designed in Houston.