Last month, potentially dangerous leaks of hydrogen gas thwarted back-to-back launch attempts.

'Nothing in this business is ever guaranteed, but this one I feel really good about, that we got that problem licked and we're not going to see a ... leak again on the next launch attempt,' said Mike Moses, a launch manager.

'And there's wood around somewhere here I can knock on,' he said, tapping the news conference table.

Because of the successful test, Nasa is now shooting for a launch attempt July 11. Endeavour is set to deliver one last piece of a Japanese space station lab.

Earlier on Wednesday, launch controllers filled Endeavour's external fuel tank to see if repairs plugged the leak. No abnormal leakage was detected during the three-hour test.

During two launch attempts in mid-June, significant amounts of hydrogen gas escaped from around a plate on the fuel tank that attaches to a vent line.

Engineers discovered a slight misalignment of the plate, and a different, more pliable type of seal, with a spring, and special washers were installed to correct the problem.

The same plate on the fuel tank that will be used to launch Discovery in mid-August also is slightly misaligned, and similar repairs will be conducted, Mr Moses said.

Engineers are still trying to figure out how the plates were installed ever so slightly tilted.

Commander Mark Polansky, who monitored the test from Houston, was pleased with the results.

He said he and his crew will return to Kennedy Space Center on Tuesday for the start of the launch countdown. -- AP