A group of Australians have sparked a Coronavirus outbreak in the ski resort town of Aspen where three Australians are refusing to be tested, despite 10 confirmed cases among the group.

But authorities in Colorado said there was nothing they could do to force the trio to undergo tests, although said they were all in quarantine.

Ski resort operators warned more cases were now likely as a result of the Australian-induced outbreak.

Two dozen Australians were part of a cluster of coronavirus infections in Aspen, Colorado. Credit:The Aspen Times/AP

Australian Melinda Williams, 60, is one of the group in Aspen, Colorado. She told Melbourne's 3AW that the original "bunch of mates" comprised around 24 people who have been on skiing holidays there every year for the last 10 years.