On Tuesday, when two international flights from Singapore and Doha were set to bring in 245 passengers, Health Minister Roger Cook said the federal government had responded favourably to the request overnight.

"We need to slow the flow," Mr Cook said.

"This is to ensure that we manage our arrivals and quarantine arrangements to the highest standards.

"If we're inundated with returnees to Western Australia, we will struggle to provide the level of care that we expect."

He said the cap would be implemented over the coming week, given various flights are already committed.

"We can't simply turn the tap off but we do want to start getting on top of it."

Daily international arrivals in Sydney were capped at 450 on Sunday while all international flights are being diverted from virus-hit Victoria and as travellers appear to be diverting from Queensland, where the state government is charging for quarantine accommodation.

WA is drafting urgent legislation that would force all returning travellers to pay for their mandatory 14-day stays.

Meanwhile, after a recommendation from the state government, ticket sales for the July 19 AFL derby between West Coast and Fremantle have been temporarily suspended.

WA is tentatively scheduled to move into phase five of eased restrictions the day before, removing all remaining limits on gatherings and allowing 60,000 capacity crowds at Optus Stadium.

But the date could be pushed back, with authorities keeping a close watch on the outbreak in Victoria.

Mr Cook said he understood derby ticket sales had already reached 30,000, which is the capacity limit under phase four.

"If we get to the end of this week and we're still not confident about the situation in regards to Victoria, then we need to push pause on phase five," he said.

The last time WA recorded a community-based infection was April 11.

No new cases were recorded overnight, leaving the tally of active cases at 12.

Australian Associated Press