WASHINGTON, July 18 -- U.S. space firm SpaceX on Monday launched supplies to the International Space Station, including a crucial docking port for future American commercial crew vehicles, and also achieved a successful rocket landing on solid ground again.

The SpaceX Dragon cargo spacecraft lifted off on the company's Falcon 9 rocket at 12:45 a.m. EDT (0445 GMT) on time from Cape Canaveral Air Force Station in Florida.

Among the cargo is the first of two international docking adapters, which will allow U.S. commercial spacecraft to dock to the station when transporting astronauts in the near future.

Its first users are expected to be the Boeing Starliner and SpaceX Crew Dragon spacecraft, which are now being developed in partnership with the U.S. space agency NASA's Commercial Crew Program and expected to begin test flights in 2017 and 2018.

The adapter, a metallic ring big enough for astronauts to fit through, also represents the first on-orbit element built to the docking measurements that are standardized for spacecraft builders worldwide, said NASA.

"It's really good we have an international standard now that anybody can build against and come dock to the station or to anything that has the same standard," David Clemen, Boeing's director of Development and Modifications for the space station, said in a NASA statement.

SpaceX had tried to deliver one international docking adapter last year, but the equipment was destroyed during a launch accident.

Overall, the uncrewed Dragon spacecraft is loaded with about 5,000 pounds (2,268 kg) of cargo for its ninth Commercial Resupply Services mission for NASA.

The payload included a pocket-size device that will allow DNA sequencing in space for the first time. The samples in this first test will be DNA from a virus, a bacteria and a mouse.

If everything goes as planned, the spacecraft will arrive at the space station in two days.

Monday's event marks the California-based company another successful first-stage rocket recovery attempt, with NASA's TV live broadcasting the booster touched down vertically on a landing zone, also at Cape Canaveral Air Force Station, minutes after Monday's launch.

"The stage sat on the pad," a NASA TV commentator said.

SpaceX achieved a soft landing on a land-based pad at Cape Canaveral last year. Since then, it had three successful landings on a droneship in the Atlantic Ocean.

The company said the reflight of its recovered rocket could occur this fall.

SpaceX is one of two U.S. companies that provide space station cargo services for NASA. The other company is Orbital ATK, whose next space station cargo launch is targeted for next month.