A Russian rocket has successfully launched an unmanned cargo ship to the International Space Station, whose crew is anxiously awaiting its arrival after the successive failures of two previous supply missions.

A Soyuz-U rocket blasted off as scheduled from Russia-leased Baikonur launch pad in Kazakhstan, placing the Progress M-28M cargo ship into a designated orbit.

The previous Progress launch in April ended in failure, and on Sunday a US supply mission also failed when SpaceX's Falcon 9 rocket broke apart shortly after lift-off.

The success of the latest launch is essential for the station programme, which has relied on Russian spacecraft for ferrying crews after the grounding of the US shuttle fleet.

The next station crew's launch has been pushed back from late May to late July after April's failure.

The supply ship is due to dock at the station currently manned by Russians Gennady Padalka and Mikhail Kornienko and Nasa's Scott Kelly on Sunday.

The ship is carrying 2.4 tonnes of fuel, oxygen, water, food and other supplies for the crew, Russian space agency Roscosmos said.

Despite the previous failures, Nasa says the station is well-stocked, with enough supplies for the crew to last at least until October.

SpaceX still hopes to meet the target of launching astronauts from US soil again aboard the Falcon-Dragon combination in December 2017, which would allow Nasa to stop buying seats from Russia to get astronauts to the space lab.