CARBIS BAY: Rising COVID case numbers and hospitalisations are a matter of "serious, serious concern", British Prime Minister Boris Johnson said on Saturday, adding he was less optimistic about reopening the country than he was last month.

"It's clear that the Indian variant is more transmissible and it's also true that the cases are going up, and that the levels of hospitalisation are going up," he told Sky News.

"Now, we don't know exactly to what extent that is going to feed through into extra mortality, but clearly it's a matter of serious, serious concern."

Johnson is expected to set out on Monday whether a planned lifting of coronavirus restrictions can go ahead on June 21, or whether rising cases will force it to be delayed.