MELBOURNE, Sept. 19 (Reuters) - Australia reported 1,607 new COVID-19 cases on Sunday (Sep 19) as states and territories gradually shift from trying to eliminate outbreaks to living with the virus.

Victoria, home to about a quarter of Australia's 25 million people, recorded 507 cases as its premier said a weeks-long lockdown will end once 70 per cent of those 16 and older are fully vaccinated, whether or not there are new cases.

Premier Daniel Andrews said the state might reach that vaccination threshold around Oct 26. About 43 per cent of Victorian residents have been fully vaccinated and just over 46 per cent of people nationwide.

"We will do so cautiously, but make no mistake, we are opening this place up. There is no alternative," Andrews said. "We cannot perennially or permanently suppress this virus. Lockdowns have been about buying time to get to 70 per cent and 80 per cent vaccination."

Many social distancing restrictions will remain and retail and hospitality venues will be limited, but people will be free to leave their house without a reason.

Andrews said the authorities aim to have 80 per cent of the state's eligible population fully vaccinated in time for the Nov 2 Melbourne Cup, leaving the door open for crowds on track at Australia's most famous horse race.

The COVID-19 plan follows a federal scheme that will end lockdowns at a 70 per cent vaccination rate and gradually reopen international borders at 80 per cent.

New South Wales has adopted a similar plan. Australia's most-populous state reported 1,083 cases on Sunday as it uses lockdowns and vaccination blitzes to fight an outbreak of the Delta variant that began in mid-June.

The state, home to Sydney, eased some restrictions on gathering on Sunday. About 52 per cent of people have been vaccinated in New South Wales.

After eliminating COVID-19 outbreaks last year through lockdowns, border closures and strict public health measures, Australia has acknowledged in recent months that it may not be able to eradicate Delta outbreaks.

The country has had just over 84,000 coronavirus cases, but two-thirds of the infections have occurred this year, mostly since June. There have been 1,162 deaths from COVID-19.