Australians stuck on a cruise ship anchored off Montevideo in Uruguay say they are terrified of being stranded for weeks or longer, as coronavirus shuts down global transport links.

Key points: Passengers were told they would only be allowed to get off the ship after all onboard had gone 14 days without a fever

Passengers were told they would only be allowed to get off the ship after all onboard had gone 14 days without a fever The price of a charter flight home for passengers on another ship then increased by roughly $3,200 per person

The price of a charter flight home for passengers on another ship then increased by roughly $3,200 per person Those passengers sent a letter and video to Prime Minister Scott Morrison urging him to cover the unexpected price increase

About 100 Australian passengers are on the Greg Mortimer, which has not been allowed to dock by local authorities after a trip to Antarctica.

Coffs Harbour woman Christine Lefeaux Waites told the ABC "six people with mild flu symptoms" had recently returned negative results for COVID-19 and passengers had been isolated in their cabins since March 22.

"I am scared and want to get home," she said.

"Morale is low and passengers do not even speak to each other. We can go on our balconies for fresh air but other than that no exercise."

Those onboard had hoped to join about 130 other Australians from a separate cruise ship, the Ocean Atlantic, on a special charter flight to Sydney on Wednesday, local time.

But in a letter to passengers, Aurora Expeditions — the company that operates the Greg Mortimer — warned people would only be allowed to get off the boat after all onboard had gone 14 days without a fever.

The letter given to passengers from Aurora Expeditions. ( Supplied )

"Unfortunately based on this news we have not been able to join our original charter or any flights currently scheduled," Aurora Expeditions managing director Robert Halfpenny wrote.

"We have deeply considered sailing to other places in the world, such as Australia, but have decided not to do this at this time because we believe we are better placed here."

The cruise departed the resort town of Ushuaia on the southern tip of Argentina on March 15, two days before the Department of Foreign Affairs urged all Australians to return home as soon as possible via commercial flights.

Many of the passengers had booked the trip years in advance and spent substantial sums of money.

"We were assured [when we left] that things were not bad and we would return if the situation changed," Ms Lefeaux Waites said.

"We did express concern ... but again Argentina had not closed its borders and no-one predicted this situation."

The dining options for passengers. ( Supplied )

Morrison Government answers another ship's call for help

Watch Duration: 1 minute 52 seconds 1 m 52 s Watch Space to play or pause, M to mute, left and right arrows to seek, up and down arrows for volume. Stranded Australian passengers call on Scott Morrison for help.

The decision to block the Greg Mortimer from docking at Montevideo has also affected the Australians onboard the Ocean Atlantic, which had been on a 20-day expedition cruise to Antarctica.

Because there are now fewer passengers to share the cost, the price of their charter flight back home has increased by roughly $3,200 per person.

After some debate, the passengers — who are mostly in their 60s and 70s — sent a letter and a video to Prime Minister Scott Morrison, urging him to cover the unexpected price increase.

The move concerned some relatives back home, who were worried the request for taxpayer assistance might anger some Australians, who had lost jobs and businesses due to the coronavirus pandemic.

According to passengers onboard the Ocean Atlantic, 109 people had announced they would pay the extra money. Some even offered to cover the cost for those who could not afford it.

But on Monday, after the video was broadcast by Australian news outlets, the Federal Government offered financial assistance.

"We are aware that [travel company] Chimu has substantially increased the seat prices," Foreign Minister Marise Payne said.

"The Government will ensure the passengers are reimbursed for this price rise."

Several people onboard have since told the ABC they were very relieved by the decision.

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Cruise ships a huge challenge for governments worldwide

Repatriating people stuck on cruise liners has proved a huge challenge for governments across the globe.

About 100 other Australians were on the coronavirus-stricken ship, the Zaandam, which is off Panama in central America.

Four people have died onboard, two have tested positive for COVID-19 and close to 200 others have reported flu-like symptoms.

Asymptomatic passengers were moved to its sister ship, the Rotterdam, over the weekend, including many of the Australians.

"All of our neighbours transferred, everyone else went and we never heard another word," said Australian passenger Shirley MacLaren, who is still travelling on the Zaandam with her husband.

Passenger Shirley MacLaren uses a controlled air pump for sleep apnoea. ( Supplied )

Both ships made it through the Panama Canal overnight and are now heading towards Fort Lauderdale, Florida, where they were expected to arrive on Wednesday, local time.

Ms MacLaren feared a controlled air pump that she used for sleep apnoea may have made her ineligible to move to the Rotterdam.

"The lack of communication has been really, really hard to cope with," she told the ABC, while confined in her cabin.

"There is no guarantee at Fort Lauderdale that we will be allowed to dock but this is an American ship.

"We are really believing there is hope we can stay onboard until a flight can be arranged for us."

Florida Governor Ron DeSantis has been in contact with the White House and local officials about the ships, calling the issue a "big, big problem".

He told Fox News he wanted to make sure South Florida hospitals were not overwhelmed if the vessels docked at port or a military base.

"We cannot afford to have people who aren't even Floridians dumped into South Florida using up those valuable resources," he said.