The head of Japan's Olympics organising committee ruled out on Thursday another suspension of the Games, despite deep disquiet at the prospect of thousands of athletes and officials arriving during a fourth wave of Covid-19 infections.

Already postponed from last year at the cost of an extra $3.5 billion, a scaled-down version of the Games, with no foreign spectators, is set to start on July 23.

But with a slow vaccine rollout, Tokyo and nine other regions under a state of emergency, and rising numbers of severe coronavirus cases, most Japanese oppose hosting the Olympics.