SYDNEY (AFP) - Australia is ready to quarantine an entire cruise ship carrying 2,000 passengers to limit the spread of swine flu, Health Minister Nicola Roxon said Thursday.

As experts warned Australia's rapidly rising number of swine flu cases could become an epidemic affecting 25 percent of the population, Roxon said authorities were closely monitoring the cruise ship Pacific Dawn.

The ship is moored off Queensland state awaiting the results of tests on three crew members and a passenger suspected of carrying the A(H1N1) virus.

The Pacific Dawn has already been blamed for a spike in Australian swine flu cases after authorities last week allowed 2,000 passengers to disembark in Sydney despite a suspected swine flu outbreak aboard.

At least 20 were subsequently diagnosed with the virus and their presence in the community is believed to have added momentum to swine flu's spread in Australia, where there are now 86 cases nationwide.

With authorities keen to avoid a similar situation in Queensland, Roxon said the entire ship, now carrying 2,000 new passengers as it waits to set out on another cruise, would be declared a quarantine zone if necessary.

"Certainly there will be no hesitation from our government or from the states and territories to take the advice of the health officials if they thought that was necessary," she told public radio.

Officials have already tightened the rules applying to cruise ships following the bungle in Sydney, treating them all as potential swine flu sites and keeping passengers aboard until they have been cleared.

Worldwide, the number of A(H1N1) cases has soared to nearly 13,400 in 48 countries, with 100 deaths, according to the World Health Organisation.