The launch of the first privately-built and operated spaceship to the International Space Station has been postponed.

California-based Space Exploration Technologies, better known as Space X, announced Tuesday it was moving the launch date from next Monday, April 30, to May 7, one week later. A spokeswoman for Space X said engineers need more time to complete tests on the rocket and review the data.

Space X will launch the unmanned, reusable Dragon capsule from Florida's Cape Canaveral Air Force Station on a mission to deliver over 500 kilograms of cargo to the ISS and its six-member crew. The crew will capture the Dragon with one of the station's robotic arms, then dock it with the orbital outpost.

After three weeks at the ISS, the Dragon is slated to return to Earth loaded with 600 tons of supplies.

Space X, owned by Internet entrepreneur Elon Musk, became the first private company to launch a spacecraft into orbit and back in December 2010. It is one of many private companies competing to replace NASA's defunct space shuttle program as a means of delivering cargo and, eventually, crews to the ISS.

The U.S. has been forced to rely on Russia's Soyuz spacecraft since retiring the shuttle fleet.