Discovery's astronauts completed a successful practice countdown aboard the spaceship Thursday, the last big test before they lift off in as little as three weeks on the first shuttle mission in 21/2 years, NASA said.

The space agency on Wednesday plans to announce a launch date after assessing the countdown test and other factors. Officials are looking at a date between Sept. 26 and 29."We clearly demonstrated that we're ready to pick up the count for real; I hope that we will be able to do that by the end of the month," Kennedy Space Center Director Forrest S. McCartney told the launch team after the test.

"It certainly sets the stage for what we're about ready to do here in just a few weeks," launch director Bob Sieck added.

Commander Rick Hauck and his four crewmates, wearing new partial pressure suits, switched dials, tested communications, monitored systems and followed all procedures scheduled during the final two hours of an actual countdown.

"Everything appears to have gone quite well," said launch control commentator Hugh Harris as the test concluded at 10:34 a.m., 34 minutes behind schedule because of minor communications problems between the craft and control center.