Officials of the National Transportation Safety Board and the Federal Railroad Administration last night discounted a television report that NTSB staffers were planning to recommend the immediate recall of about 20,000 rail cars to have the wheels replaced.

An ABC TV network news report last night said that safety board staffers believed the Southern 70-ton wheels should be replaced because they allegedly break apart under extreme heat.

The report also alleged that the wheels in question were involved in the recent derailments in both Waverly, Tenn., and Bowling Green, Ky.

But federal officials said last night that there was no conclusive data to support the ABC report.

"The report was premature," said Kay Bailey, Acting Chairman of the NTSB. "None of this information has come to us from the staff."

She said that under the present plan, when the staff decides to make a recommendation, the entire board would vote on the proposal almost immediately. But, she hastily added, no proposals have been made yet.

At the Federal Railroad Administration, Chief Counsel and Acting Safety Chief Ray James also said the ABC report appeared premature.

"In Waverly," James said, "it is pretty clear that the wheel was the cause, out we don't know what caused the wheel to crack. We think the handbrake may have been left on."

In Bowling Green, he said, "We thought the cause was a cracked wheel, but now we're not so sure."

He said that in both cases investigators are looking for something that "could have put additional stress on the wheels."

The ABC report says that if the government was to order 20,000 cars in to the replacement of some 150,000 train wheels, the cost would be about $105 million, the largest recall in rail history.