MELBOURNE, March 14 (Reuters) - Australia's prime minister cancelled plans to go to a rugby game on Saturday after a senior minister was diagnosed with COVID-19, while the nation's treasurer called a second crisis meeting over the rapidly growing economic threat from the coronavirus.

Treasurer Josh Frydenberg was set to hold a phone hook-up with Reserve Bank of Australia officials and financial regulators on Saturday, his spokeswoman said, without elaborating on what would be discussed.

It will be the second crisis meeting involving the central bank, the country's prudential regulator and markets watchdog and follows the government's A$17.6 billion ($10.9 billion) stimulus plan this week to prevent the coronavirus outbreak triggering a recession.

Australia has 197 confirmed cases of COVID-19, including three deaths.

Prime Minister Scott Morrison on Friday called for an end from Monday to all non-essential gatherings of more than 500 people, including sporting and cultural events, and urged people to reconsider overseas trips.

While the request did not apply to businesses and public transport, some companies have asked staff to work from home.

In the biggest such move, Australia's top telecommunications company, Telstra Corp Ltd, on Friday ordered around 20,000 staff, 70% of its workforce, to work from home starting on Monday until at least the end of March, a spokesman said.

Ahead of the ban on big gatherings, the Australian Formula One Grand Prix, scheduled for this weekend, was cancelled. A concert by UK pop start Robbie Williams that was to take place at the race track on Saturday was also called off, organisers World Tour said.

"Gutted I'm not able to perform tomorrow in Melbourne," Williams said on Friday on Twitter.

Morrison had planned to attend a rugby game on Saturday but decided late on Friday not to go after Home Affairs Minister Peter Dutton was diagnosed with COVID-19. They had attended a cabinet meeting together on Tuesday.

The prime minister said he had received medical advice that only people who had been in contact with Dutton over the previous 24 hours needed to self-isolate.

Australia's Chief Medical Officer Brendan Murphy said on Saturday that it was "extremely unlikely" anyone who was at Tuesday's cabinet meeting would have contracted the infection from Dutton.

However, U.S. President Donald Trump's daughter Ivanka and U.S. Attorney General William Barr, who met Dutton in Washington on March 6, decided to work from home on Friday.

New Zealand minister Tracey Martin, who also attended the meeting in Washington, is self-isolating while awaiting results from a coronavirus test, New Zealand media reported on Saturday.

($1 = 1.6176 Australian dollars) (Reporting by Sonali Paul; Editing by Daniel Wallis)