Instead, as Japanese television footage vividly showed, Mr. Bush, who already looked tired, became suddenly and dramatically ill.

He threw up on his shirt and suit jacket, rolled backward in his chair and tilted toward Mr. Miyazawa, who sat with Mrs. Bush to his left, and appeared about to collapse when a Secret Service agent vaulted atop the dinner table and a second eased him to the floor.

"All of a sudden, the music stopped, and people froze," said Nobuaki Tanaka, the director of the Foreign Ministry office that handles relations with North American countries. "We were so worried about the President. People were saying, 'Where's the ambulance?' Everyone applauded when the President stood up. I was so relieved."

Mr. Bush was on the floor for some time, while a worried Mr. Miyazawa and Mrs. Bush hovered over him and aides removed his jacket. An official said an uncomfortable silence descended over the room until Mrs. Bush, convinced that her husband was not seriously ill, offered reassurances.

Mrs. Bush, who stayed behind at the dinner, jokingly told the crowd later that the President had probably been sickened by the drubbing he took in tennis with the Emperor and the Crown Prince.

Today, Mrs. Bush's press secretary, Ana Perez, told reporters that the First Lady heard the President joke as he lay on the floor.

"He said to the Prime Minister, 'Why don't you roll me under the table and I'll sleep it off while you finish the dinner,' " she said.