CAPE CANAVERAL, AUG. 30 -- NASA tonight postponed the scheduled Saturday launch of space shuttle Columbia because of an electronic part failure on one of the four telescopes in the shuttle's cargo bay.

The launch will take place "no earlier than next Wednesday," said Bruce Buckingham, a NASA spokesman.

Engineers had been unable to establish a telemetry link with an X-ray observatory, one of the four telescopes carried in the cargo bay of Columbia, and traced the problem to an "avionics box" on the telescope.

"We're not exactly sure about how we're going to fix that box," Buckingham said.

The launch of the $150 million Astro observatory aboard Columbia already has been delayed five years. It originally was scheduled for March 1986, but was postponed after the Challenger disaster in January 1986. The mission was rescheduled for last May 30, but when fuel was pumped into the shuttle tanks, a leak was discovered.

The new problem surfaced after Columbia's payload bay doors were closed Wednesday night.

Program scientist Ed Weiler said full communication contact with the observatory is necessary for launch. The scientific returns from the flight will not suffer if the flight is delayed a few days, he said.

"A few days' slip really won't affect it at all. It really won't change it," Weiler said.

Once aloft, the observatory will probe some of the hottest known objects in the universe during the nine- or 10-day mission. A comet and supernova are among the approximately 150 targets.