CAPE CANAVERAL (Florida) • An unmanned H-2B rocket has blasted off from Tanegashima island in southern Japan to send a cargo ship to the International Space Station.

The delivery of about 4.5 tonnes of supplies for the six-member station crew took on fresh urgency after a botched Russian cargo run on Dec 1 and additional delays in the return of Nasa contractor SpaceX to flight following an unrelated accident.

The rocket, carrying Japan's HTV-6 cargo ship, blasted off on Friday night, flying over the Pacific Ocean on its way to space.

The capsule is expected to reach the station, a US$100 billion (S$142 billion) laboratory flying about 400km above Earth, on Tuesday.

In addition to food and supplies, the capsule is delivering six lithium-ion batteries and adapter plates, weighing about 1,360kg, which are needed for a planned upgrade of the station's electrical system. The batteries will be installed during upcoming space walks, said Nasa launch commentator Dan Huot.

The Japanese HTV capsules are among four supply ships that fly to the space station, a project involving 15 nations. However, two of the four freighters are grounded following accidents.

A Russian Soyuz rocket failed to put a Progress capsule into orbit on Dec 1 due to a problem with the booster's third-stage engine. The capsule burned up as it fell back into Earth's atmosphere, with debris crashing to the ground.

Tech billionaire Elon Musk's SpaceX is recovering from a launch pad explosion on Sept 1 that destroyed a Falcon 9 rocket and a US$200 million Israeli communications satellite. SpaceX now expects to return to flight in January.

REUTERS