Prime Minister Scott Morrison said the package could help six million Australians as he unveiled the federal government's third and biggest round of economic stimulus on Monday.

"We want to keep the engine of our economy running through this crisis," he said.

The federal government will give the $1500 allowance to businesses and not-for-profit organisations that have taken a 30 per cent hit to turnover because of the coronavirus.

Companies turning over more than $1 billion will be eligible if they have taken a 50 per cent hit.

The subsidies will last for six months, with full-time, part-time and casual workers who have been with their employer for at least 12 months eligible.

Sole traders have also been included in the package.

Payments will flow to businesses in the first week of May, with the program to start from March 30.

Workers stood down since March 1 will be able to qualify for backdated payments.

New Zealanders on temporary working 444 visas and migrants eligible for welfare are also included.

Mr Morrison said some countries would face economic collapse or hollowing out in coming months as the disease spreads globally.

"In the very worst of circumstances, we could see countries themselves fall into chaos - this will not be Australia," he said.

Parliament could sit as early as next week to pass legislation related to the "job-keeper" payment, with Labor likely to support the overall package.

Coupled with support for banks, the government has so far set aside $320 billion, or 16.4 per cent of GDP, to deal with the fallout from the virus.

ACTU secretary Sally McManus said unions were glad the government had listened to the campaign for a wage subsidy program, but were concerned the $1500 was not enough.

"We believe that allowing this amount to increase up to the median wage of $1375 a week is what is needed," she said.

"We also want to ensure all casuals who could have reasonably expected to work now but have lost their jobs because of the pandemic are covered."

There was a case for workers who had been let go to be re-employed, she said.

As well, there could be cash flow issues for many workers whose employer may not survive another six weeks without immediate support.

Treasurer Josh Frydenberg said Australia was facing an economic and health war.

"The past weeks have been tough but the weeks ahead will be tougher," he said.

"Australians know that no matter how great the challenge is, our government has their back."

Business Council chief executive Jennifer Westacott said the subsidies were a fair way of making sure employees stayed connected to employers during the crisis.

"This huge package will keep people in jobs and vitally, make sure Australia is ready to rebuild quickly once this challenge passes," she said.

Greens leader Adam Bandt believes Australia should guarantee 80 per cent of all workers' pay.

"This wage subsidy is too little, too late," he said.

Australian Associated Press