Prime Minister Scott Morrison has defended Australia's lockdown strategy for tackling the coronavirus, saying it would stay until at least 70 per cent of population is fully vaccinated, as daily infections break records.

Sunday's 914 cases of the highly infectious Delta variant surpassed the previous high of 894 a day earlier, Reuters reported.

“You can't live with lockdowns forever and at some point, you need to make that gear change and that is done at 70pc,” Morrison said in a television interview on the Australian Broadcasting Corp.

Lockdowns are a key element of the federal government's strategy to rein in outbreaks until the 70pc level is reached, with borders being re-opened gradually when the figure climbs to 80pc.