With the Olympics cancelled, the tune has changed.

Japan is struggling to hold the line against the coronavirus and is on the brink of crisis with medical experts particularly worried about preparations in Tokyo, officials said on Wednesday, raising the prospect of emergency lockdowns.

"We are barely holding the line and remain at a critical point where virus cases could surge if we let down our guard," Prime Minister Shinzo Abe told a parliamentary committee.

Economics Minister Yasutoshi Nishimura said infectious disease experts were alarmed about medical preparations in Tokyo.

"Many experts expressed very strong sense of crisis and opinions over the spread of infections in Tokyo and the current state of medical preparedness," Nishimura told reporters.

"We must prevent infections from spreading further no matter what. We have come to the edge of edges, to the very brink.”