Engineers from the US space agency NASA think they have discovered the cause of a hydrogen leak which twice delayed a high-profile shuttle launch this month, according to the agency.

It may now be all systems go for the space shuttle Endeavour, which is waiting to embark on its final mission to the International Space Station, after a dodgy gas line connection was uncovered during tests.

NASA program manager John Shannon said a misaligned plate linking the hydrogen gas vent line with the external fuel tank had been causing the leak, which was first detected during fueling.

The Endeavour is set to carry a seven-member crew on a 16-day voyage to install a platform on the ISS, allowing astronauts to conduct experiments in the vacuum of space, 350 kilometers (220 miles) above Earth's surface.

To install the equipment five space walks are planned, lasting some 32 and a half hours. It is the last of three missions to assemble the Japanese Kibo laboratory aboard the orbiting space station.

The race is on to finish construction before NASA ends its shuttle missions in September 2010.

"Technicians are preparing to test the repair plan by filling Endeavour's external tank with liquid hydrogen and liquid oxygen in the next week and a half," NASA said in a statement.

Another launch attempt is scheduled for July 11.