Chelsey Martin, Australia's consulate-general in Los Angeles, issued a stark message on Thursday to the "tens of thousands" of Australians who live within her jurisdiction in America's southwest states.

Qantas and Virgin Australia are about to cut flights from the US to Australia while United Airlines will have a limited schedule.

"Whatever your circumstances, given the escalating COVID-19 crisis I wanted to reach out and encourage any Australians wishing to go home to do so as soon as possible," Ms Martin said in a video message posted on the LA consulate's Twitter page.

"After the end of this week, commercial flight options will be incredibly limited.

"Qantas' final scheduled flight is out of LAX (Los Angeles) on Friday, the 27th of March.

"Virgin's final scheduled flight out of LAX is on Sunday the 29th of March.

"United Airlines has advised us that they will continue with a limited flight schedule from San Francisco to Sydney in the weeks ahead, but the situation is changing rapidly and I would encourage anyone who is still deciding whether or not they would like to return to Australia, not to delay taking that decision.

"These are unprecedented and anxious times for many."

Ms Martin said the LA consulate would remain open "around the clock" to provide consular assistance.

Australians were also being urged to follow the consulate on Twitter, Facebook and Instagram for information updates.

Australian Associated Press