A light cord that got in the way while a work platform was being removed caused the chain-reaction accident last month that ruined a $4 million fuel tank on the country's last Atlas-Centaur rocket, a space agency official said yesterday.

"This tank cannot be repaired; it was essentially destroyed," said Richard H. Truly, the head of space flight for the National Aeronautics and Space Administration.

Four workers were slightly injured on the launch pad at Cape Canaveral, Fla., when the Atlas-Centaur was punctured by the legs of a workstand that had fallen from a platform above. The accident will delay the launching of the $78 million rocket for up to one year, Truly told the House space science subcommittee.

Truly and James B. Odom, head of a NASA board investigating the accident, gave an interim report to the subcommittee at a hearing that delved into the destruction by lightning of an Atlas-Centaur and its communications satellite cargo on March 26, a $161 million setback for NASA.

Lt. Col. John D. Warburton, chief Air Force weather officer at Cape Canaveral, told the panel that his team's recommendation of a "go" for launch that day was "basically on the hairy edge" of the rules, because the weather was so "marginal."

But the Air Force meteorologists, he said, did not inform NASA's launch team of this because they thought the situation was obvious. The weather was stormy and an investigation board in May concluded that the NASA and Air Force teams used poor judgment and violated NASA weather guidelines in launching.