MELBOURNE—Australia is sticking to plans to start re-opening to the rest of the world only from the middle of next year, officials said on Sunday, resisting mounting pressure to end the closure of international borders. In March 2020, Australia closed its borders to non-nationals and non-residents and has since been allowing only limited international arrivals, mainly citizens returning from abroad. “All the way through we will be guided by the medical advice,” Prime Minister Scott Morrison said at a televised briefing. “We will be guided by the economic advice.” Earlier in the day, Treasurer Josh Frydenberg told the Australian Broadcasting Corp (ABC) that he believes the medical advice to keep the borders closed had “served us very well through this crisis.” Australia’s border closure, combined with virus control measures such as snap lockdowns, swift contact tracing, and public health compliance has seen the island country enjoy some of the world’s …