SYDNEY, July 6 (Reuters) - The premier of Australia"s New South Wales (NSW) said on Tuesday she aims to decide within the next 24 hours whether to extend a COVID-19 lockdown in Sydney that is due to end on Friday as new infections dropped in the country"s most populous state. Just 18 new locally acquired COVID-19 cases were detected in NSW on Tuesday, half of the previous day"s number. But Premier Gladys Berejiklian said the decision would also take into account her administration"s determination to make the current lockdown in the city of five million people the last, as it aims to step up vaccinations. "That will factor into our decision-making as to whether it (the two-week lockdown) finishes on Friday or whether we continue for a period longer," Berejiklian told reporters. "I hope to be able to communicate to the community tomorrow on what next week looks like." Sydney went into a hard lockdown on June 26 to quash the latest flare-up - an outbreak of the Delta variant of COVID-19 - but officials have been frustrated after finding new infections linked to illegal gatherings and people flouting social distancing rules, raising prospects of an extension. Of Tuesday"s cases, 16 were either in isolation throughout or for part of their infectious period. Two cases spent time in the community while they were infectious. With Sydney battling its worst COVID-19 outbreak of 2021, total infections in the flare-up crossed 330 since the first case was detected nearly three weeks ago in a limousine driver who transported overseas airline crew. Speedy contact tracing, lockdowns, tough social distancing rules and a high community compliance have kept Australia"s COVID-19 numbers much lower among developed economies, with just over 30,800 cases and 910 deaths since the pandemic began.