The US space shuttle Endeavour has soared into orbit on a mission to install a Japanese-built porch for science experiments on the International Space Station.

After more than a month's delay, the shuttle launched on Wednesday, carrying seven astronauts.

It was the sixth attempt to launch Endeavour by US space agency Nasa and was a welcome sight for shuttle workers who had to overcome gas leaks last month and thunderstorms recently.

The launch also fell on the eve of the 40th anniversary of the liftoff for man's first moon landing.

Mark Polansky, Endeavour's shuttle commander, and his crew are expected to reach the space station on Friday.

Five spacewalks are planned to hook up the new porch for the Japanese laboratory and perform other station work.

The flight is scheduled to last 16 days.