Premier Mark McGowan has faced heavy criticism after appearing to use an economic justification for the continued border closures.

Asked whether WA would consider a travel bubble with South Australia and the Northern Territory, where case numbers are similarly low, the premier said there was "no benefit" and it would only result in WA losing tourist dollars.

WA senator and finance minister Mathias Cormann on Friday accused Mr McGowan of keeping the borders closed for the purposes of economic protectionism, which he said was "explicitly prohibited in the Australian Constitution".

Mr McGowan shrugged off the attack, highlighting the federal government's short-lived intervention in support of businessman Clive Palmer's legal challenge against WA's border closures.

"Had they been successful when they were doing that, when the virus was raging in Victoria, chances are the pandemic would have come back to Western Australia and the economy would have been devastated," he said.

"I'm very comfortable our cautious approach has kept the health outcomes good and the economic outcomes outstanding within Western Australia."

With all other states and territories set to reopen by Christmas, the premier again refused to put a date on when WA's border restrictions might end.

But he said the removal of lockdown restrictions in Victoria would influence how things progressed in coming weeks and months.

"The advice from the chief health officer is they'll watch what happens in Victoria and see how it goes and whether there's any third wave," he said.

"My fear is if you act too early, if you're not cautious, the virus comes back and we end up in a situation that Melbourne has been going through for months and months.

"A bit of caution goes a long way ... that's why we're doing this."

WA has 20 active cases after two recoveries overnight.

The numbers have been inflated by an outbreak on the Patricia Oldendorff bulk carrier off Port Hedland.

Nine people remain on the ship as essential crew, seven of whom have tested positive.

There are also a dozen crew members in quarantine at the fenced-off Hedland Hotel and 10 of them have tested positive.

Mr McGowan on Thursday said several crew had already recovered.

The ship, carrying 20 Filipino nationals and the captain, arrived from Manila on September 16 and is anchored eight nautical miles off WA's northwest coast.

Authorities are confident it will set sail next week.

Australian Associated Press