A gas leak in a steering engine compartment was sealed by technicians Friday, another step toward clearing the space shuttle Discovery for launch in late September or early October.

Working in cramped quarters in Discovery's up-ended cargo bay, the workers bolted a clamshell-like device on a 1/2-inch diameter fuel line that was detected leaking nitrogen tetroxide gas more than a month ago.Once the 2-inch clamp was in place, the technicians filled it with a sealing compound. Then they subjected the line to pressure tests, and NASA spokesman Karl Kristofferson reported initial data indicated the leak had been plugged.

He said the seal would be monitored for several days to be sure there was no additional leakage.

If the seal holds as expected, and if initially encouraging results of a solid fuel booster rocket test in Utah hold up, the space agency may set a date next week for launching Discovery on the first shuttle mission since Challenger exploded and killed its crew of seven on Jan. 28, 1986.

Officials have been considering a launch in late September or early October, with Sept. 29 listed as one internal planning date.

An intentionally flawed booster was fired for two minutes Thursday at the Morton Thiokol plant in Utah in the fifth and final pre-flight test of the redesigned rocket. A faulty joint in a booster was blamed for the Challenger accident.

"We're ready to fly; it looks like an absolutely great test from top to bottom," said Royce Mitchell, NASA's solid rocket booster project manager.

However, officials said that while initial results looked great, it would take several days to thoroughly analyze the test data.

To reach the nitrogen tetroxide leak, workers Wednesday used an electric router to drill holes through the rear wall of Discovery's 60-foot-long cargo bay and through the adjoining hull of a steering engine compartment.

The tiny leak was 12 inches from the newly drilled access panels, on a fitting in a vent line.

Because Discovery is standing vertically on the launch pad, the rear wall of the cargo bay is parallel to the ground, forcing the technicians to work on their hands and knees.

They worked in cramped quarters surrounded by a tent-like canvas to prevent loose debris from reaching other areas of the shuttle.

When the leak was discovered more than a month ago, officials at first feared they might have to move Discovery off the launch pad to a hangar for repairs, a move that could have delayed the launch for as much as two months, into November.

But engineers came up with the innovative idea for making the fix on the pad.

The repair job was delayed until after the launch team conducted a successful test firing last week of Discovery's three liquid fuel main engines.

The leak is in a separate engine system used to steer the shuttle in orbit.