Space shuttle Discovery blasts off

Space shuttle Discovery has blasted off with seven astronauts aboard on one of Nasa's final servicing missions to the International Space Station.

With a brilliant flash of light and a thundering roar, the shuttle lifted off shattering the pre-dawn calm around the Kennedy Space Center in Florida.

"Enjoy the ride," shuttle test director Laurie Sally radioed the crew minutes before lift-off.

The shuttle is carrying an Italian-built cargo hauler filled with equipment, experiments, food and supplies for the space station, which is expected to be finished in September after 12 years of construction about 220 miles (355 km) above Earth.

The United States plans to stop flying its trio of space shuttles after three more missions to stock the outpost with spare parts and gear too big or bulky to fit on other spaceships. The shuttles, which can carry about 50 tons to the station's orbit, are being retired due to cost and safety concerns.

Nasa will then turn over cargo deliveries to two commercial firms - privately held Space Exploration Technologies of California and Orbital Sciences Corp of Virginia. Station partners Russia, Europe and Japan also have vessels that can haul cargo to the outpost.