The US track and field team plans for a pre-Olympic camp in Japan has been scrapped over concerns about safety during the pandemic, officials said.
US athletes were supposed to train in Chiba, outside Tokyo, before the pandemic-postponed Games open on July 23.
But the Chiba regional authority said the US team cancelled "because of concerns over athlete safety as the coronavirus pandemic continues around the world with no prospects of winding down".
"Although the cancellation is extremely regrettable, we think it is the best decision ... given the current situation," the region said.
The US team (USATF) confirmed that it had scrapped plans for pre-Games training and was encouraging it athletes to stay in the US and train.
Pre-training camps across Japan have been cancelled either by prospective host towns or the athletes involved over virus concerns as the country battles a fourth wave of infections.
Tokyo and several other parts of Japan are under a state of emergency, and the government is facing pressure over its comparatively slow vaccine roll-out among wealthy nations.
Organisers say anti-virus measures will ensure the Games are held safely and point to a string of recent test events, including some with international participants, that were held without producing virus clusters.
The Japanese public as well as some of its top athletes, however, remains opposed to holding the Games this summer, with most favouring cancellation or a further delay.