The extra time is needed to complete routine launch preparations and fix 93 wiring defects found on Atlantis during extensive inspections that led to a five-month grounding of the agencys $8 billion shuttle fleet last year.

"In order to accommodate the wiring inspections and repairs on Atlantis, well have to spend more time than originally scheduled in the shuttle hangar," said Kennedy Space Center (KSC) spokesman Joel Wells.

The outfitting of Atlantis with twin solid rocket boosters and a 15-story external tank as well as a subsequent move to a launch pad at KSC -- will have to be pushed back as a result, making the March 16 launch date impossible to meet.

Senior NASA officials decided earlier this month to stage the maintenance mission on Atlantis when it became apparent the long-delayed launch of the crucial Russian control module for the station would be delayed until late this summer.

The reason: The Russian tug now keeping the outpost in an orbit is only certified to fly through the end of March, and while no major problems are expected, NASA wants to make sure the station remains in good flying condition through the end of the year.

Still in its infant stages, the seven-story station now consists of two building blocks: The Russian tug, dubbed "Zarya," or "sunrise," and a U.S. docking module that eventually will serve as a gateway to other parts of the outpost.

NASA originally had intended to launch Atlantis and a seven-member crew to do maintenance work on the Zarya tug and outfit the Russian control module named "Zvezda," or "star" after its launch.

An upgraded version of the central core of Russias space station Mir, the Zvezda module is considered one of the most important parts of the station.

About the size of a city bus, it is equipped with a crucial propulsion system that will be needed to keep the station in space when the Zarya tug eventually runs out of fuel. In addition, it will double as living quarters for initial research crews.

The type of Russian rocket slated to carry the Zvezda module aloft, however, suffered explosive launch failures in July and October of 1999. As a result, the Zvezda module now is facing a launch delay until at least August. That prompted NASA to split the already planned shuttle Atlantis mission in half.

Part two of the mission, however, probably wont be launched now until at least September or about a month after the Zvezda module finally thunders aloft.

Consequently, NASAs shuttle flight schedule for the coming year which was supposed to include five other station assembly missions will encounter significant delays.

The launch schedule still is being ironed out, but its possible that only two of the additional five missions will be launched this year. The others probably will be pushed into the year 2001.

The stations first full-time resident crew, meanwhile, will remain grounded until the fall of this year. Now scheduled to fly in May, its unlikely the crew which includes U.S. astronaut William Shepherd and Russian cosmonauts Sergei Krikalev and Yuri Gidzenko will board the outpost before October.

A joint project being carried out by space agencies in the U.S., Russia, Canada, Europe, Japan and Brazil, the station construction work is considered by many to be one of the most complex engineering endeavors of all time.

Once completed, the 480-ton outpost will span an area in space nearly as large as two football fields, providing researchers from 16 nations with world-class orbital laboratories for a decade or more.