Commercial space company SpaceX is delaying the launch of a new cargo capsule to the international space station because of software issues, officials said Wednesday. Already three months behind its initial schedule, the launch of the company’s Dragon spacecraft had been set for this coming Monday, but the company and NASA are continuing to test and verify the software, said SpaceX spokeswoman Kirstin Brost Grantham.

If SpaceX’s Falcon 9 rocket cannot launch from Cape Canaveral by May 10, the company will have to wait at least until late in the next week to try.

A Russian Soyuz spacecraft is slated to lift off from Kazakhstan on May 15 with three new space station crew members, and it will need to be safely docked at the station before the Dragon can attempt to approach.

The SpaceX launch is a critical moment for NASA’s new strategy of paying private companies to deliver cargo to the 16-nation orbiting outpost, which is slated to operate through at least 2020. SpaceX has a $1.6 billion NASA contract to fly 12 cargo missions to the station. Orbital Sciences of Dulles holds a similar contract and is developing a rocket for a test flight this summer from Wallops Islands, Virginia.

While the SpaceX mission is explicitly a test, the Dragon capsule will carry 1,100 pounds of food, water and other supplies to the space station. Since NASA retired the space shuttle last year, the agency has relied on spacecraft from Russia, Europe and Japan to resupply the station. Interest in the mission is high. Grantham said 430 media representatives had signed up to watch the launch, a “very large number for an unmanned flight,” she said.