An unmanned Russian cargo spacecraft has failed to dock with the International Space Station due to a technical failure, Russian space officials said on Tuesday.

The Progress cargo ship separated from the station Sunday to perform engineering tests and try out a new docking system and was due to dock with the station early Tuesday.

Russia's Mission Control did not name the specific cause of the failure, but said they are looking into it.

It said the spacecraft will attempt another docking on Sunday.

Japan's HTV3 cargo ship is due to reach the station on Friday, and the Russian Space Agency said in a statement that the troubles with the Progress vessel will not prevent the Japanese ship from docking.

There are currently six people on the Space Station: three Russians, two Americans and a Japanese astronaut.