The last remaining restrictions on gatherings within the state's borders had been due to end last month, allowing 60,000 capacity crowds at Optus Stadium and the removal of the two square metre rule at pubs and other venues.

But WA's chief health officer has again recommended delaying the move to phase five, citing concerns over outbreaks in the eastern states.

Premier Mark McGowan says it won't come into effect until August 29 at the earliest.

"As a nation, we have entered the most dangerous phase of this pandemic," he said on Friday.

"Even though WA has not had a community case of COVID-19 since April (12), we need to remain on high alert given what is happening across the country."

The decision comes after South Australia brought back some restrictions and Victoria introduced the most severe lockdown the nation has seen during the pandemic.

Mr McGowan said the state would do everything it could to keep its hard borders in place as its legal battle with Clive Palmer continued.

The premier also announced new testing rules for truck drivers who are still able to enter the state to provide essential goods and services.

From next week, any truck driver entering WA will have to provide evidence of having recorded a negative COVID-19 test result within the past seven days. Any driver who fails to provide that proof will be ordered to have a test within 48 hours.

WA again recorded no new positive tests on Friday, leaving the state with six active cases.

Australian Associated Press