CANBERRA, June 27 (Reuters) - Australia lowered its projections on Sunday for population and economic growth over the next 40 years due to the impact of the COVID-19 pandemic. Canberra closed its international borders in March 2020 to all but citizens and permanent residents in an attempt to prevent the spread of the virus. The government says it will only reopen to migrants when it believes it is safe to do so. Australia now expects its population to total 38.8 million by 2061, down from its last forecast in 2015 estimate when it saw it hitting 40 million by 2056. Its population currently totals 26 million. "The economy will be smaller and Australia’s population will be older than it otherwise would have been, with flow-on implications for our economic and fiscal outcomes," Australia"s Treasurer Josh Frydenberg will say on Monday, according to extracts of a speech seen by Reuters. Population growth has been the primary driver of Australia"s economic growth in recent decades. But with growth slowing and its population growing older. Canberra said it now expects its economy to grow at 2.6% a year over the next 40 years, compared with its previous forecast of 3% a year. Reporting by Colin Packham Editing by Gareth Jones Our Standards: The Thomson Reuters Trust Principles.