U.S. Ambassador Alfred L. Atherton Jr. said today that he had not been able to provide Washington with more accurate information on the condition of dying Egyptian president Anwar Sadat immediately after his shooting because a senior official initially had given him erroneous information.

Commenting on a report this morning in The Washington Post that he had misinformed the State Department, Atherton told a group of American reporters that he was first told by an Egyptian "senior official," whom he refused to identify, at about 2:30 p.m. local time that Sadat was not mortally wounded.

This was just 10 minutes before the president officially was pronounced dead at Maadi Hospital, although Sadat was unconscious and in extremely serious condition upon arriving there at 1:20 p.m.

"The present information, he the official said, was that the president had been wounded in the body, but at that point he didn't think it was fatal," Atherton said.

The American ambassador, who was at the military parade where Sadat was assassinated, said he did not actually see Sadat being shot and mistook another person lying on a stretcher for Vice President Hosni Mubarak.

"I saw a figure in Egyptian general's uniform similar to Mubarak's being carried out seriously wounded, and we speculated it might be Mubarak," he said.

The following is the account he gave of the hours between Sadat's shooting, which he put at about 12:50 p.m., and the announcement of his death shortly before 8 p.m. local time:

After getting off the floor of the parade stand where he had thrown himself, Atherton stayed behind to see what he could learn about who had been shot. He relayed by car radio his first report to the embassy's deputy chief of mission, Henry Precht, at about 1:20.

Precht, who had already established an open line to the State Department, passed on Atherton's initial information.

Then at 2:30 p.m., after Atherton returned to the embassy, he got word from the "senior official" that Mubarak was "okay" and that Sadat was wounded but not fatally.

Shortly afterward, he received phone calls from former president Jimmy Carter and Nancy Reagan, who was having difficulty getting through to Sadat's wife, Jehan. He passed on his information to them with the warning that "we have to be a little careful until we receive an official report or medical bulletin."

Reports began circulating in the capital around 4 p.m., and CBS, among others, was announcing that Sadat was dead, but Atherton said he refused to accept the reports because they were not official.

"I took the position it was not the job of the U.S. Embassy to confirm whether the president was killed or not . . . . We had nothing official and I took the position we shouldn't go out" saying he was dead before the Egyptians did, he said.

"At 5 p.m., when word got out of the Cabinet meeting, we began to suspect the reports of Sadat's death were true," he continued.

He said he had tried to make contact with various members of the Cabinet to get more information on Sadat's condition but failed to reach anyone.

Not until about 7:30 p.m., 20 minutes before Mubarak went on television to announce Sadat's death, was Atherton officially informed that he was dead.

By then, however, state-run television had for nearly two hours been featuring readings from the Islamic holy book, theKoran -- a sure indication that the president had died.

Atherton said he did not think he was "deliberately misled" by the first official. He did not say precisely when he finally relayed to Washington the information that Sadat was dead. But it seemed from his account that he had waited until being officially informed, or five hours after Sadat had been officially pronounced dead.