Prime Minister Scott Morrison announced on Friday there had been a breakthrough on border blockages, which have been causing chaos for regional communities.

National cabinet had agreed to develop a nationally consistent approach to agriculture worker restrictions, and ensure border communities could access critical health care.

The expert medical panel will also develop a definition of what a coronavirus hotspot is, to deter states from arbitrarily closing their borders to areas without cases.

It comes after Queensland closed its borders to the ACT and classified it as a coronavirus hotspot, even though the territory had recorded no coronavirus cases for weeks. South Australia is also forcing ACT residents to quarantine for 14 days.

However, the definition would not be legally binding.

"I'd say that as a process of transparency, letting the sunshine in, if there was a clear definition of what a hotspot is, then it would be odd to operate outside of that. And if people were operating outside of that, then that would be very clear," Mr Morrison said.

However, Mr Morrison warned states could be forced to foot the bill for supporting industries impacted by their decisions.

"A very good example is what's happening with flight network subsidies, aviation network subsidies," he said.

"Now, we've been supporting those now for many, many months. But I have been fairly candid and open with the states and territories that where there is a need for further subsidies to support aviation networks in place, that is as a consequence of state borders, then obviously we would be raising that with the states to to share that load, given the decisions they've made.

"I'm sure weighing up the economic costs of that in making the decisions they have on health issues, that they would be more than prepared to meet the costs of dealing with some of the impacts of those decisions."

Aviation and tourism industry leaders on Thursday pleaded with state and territory leaders to find a way forward on border closures.

Australian Airports Association chief executive James Goodwin said airports across the country were losing around $300 million per month in fixed costs. Canberra Airport has warned it could be forced to shut for further days unless interstate travel resumes soon.

Meanwhile, the Morrison government continues to resist calls to relax the cap on Australians returning from overseas, as more than 18,000 travellers remain stranded abroad.

A parliamentary inquiry heard on Thursday around 18,800 people had registered with the Department of Foreign Affairs and Trade as wanting to return to Australia, but were finding it tough because of the cap.

National cabinet last month slashed the number of weekly overseas arrivals permitted to 4000, to ease the burden on state hotel quarantine facilities.

Labor's foreign affairs spokeswoman Penny Wong said the Commonwealth needed to assess whether states and territories had any additional capacity to quarantine return travellers.

"Many have been stranded since the borders first closed and Labor has raised hundreds of cases of people in desperate circumstances with the Foreign Minister," Senator Wong said.

"Thousands of Australians who the government themselves say are vulnerable are trying to get home. This must be an incredibly stressful time for them, and we urge the government to offer all the support they can including access to clear and timely information and financial assistance where required.

"Scott Morrison should also be talking with state and territory leaders about what capacity they may have to help these Australians quarantine safely at home in Australia."

However, Mr Morrison said now was not the right time to ease restrictions, given the continuing outbreaks in Sydney and Melbourne.

"It has been the NSW government, particularly at Sydney Airport, that bears the biggest load when it comes to inbound arrivals," Mr Morrison said.

"It's our view and of course the other state governments who are affected that right now, it is not the wise decision to lift those caps."

The decision would be reviewed again in two weeks. Mr Morrison said once the Victorian and NSW outbreaks were more under control, he hoped to increase the caps.

Foreign Affairs Minister Marise Payne, Home Affairs Peter Dutton and Defence Minister Linda Reynolds had been tasked with finding ways to help Australians stuck overseas, which would be considered by the Prime Minister and Treasurer, Mr Morrison said.

"But right now, on the balance of risk, on the balance of risk, we need to keep those caps where they are," Mr Morrison said.