The torch's passage through London, Paris and San Francisco has been marred by protests from human rights campaigners.

This morning the torch arrived in the Argentine capital Buenos Aires, where more protests are expected on its only Latin American appearance.

The torch is due in Canberra on April 24 but Dr Nelson has told ABC Radio's AM program that it may not make it that far.

"I wouldn't be surprised if the IOC (International Olympic Committee) made the decision not to continue with the relay," he said.

"If you apply the prism of common sense to this, they have obviously had difficulty now in three countries, and it should be no surprise that there are likely to be protests with further torch relays."

ACT Chief Minister Jon Stanhope says the cost of staging the Olympic torch relay in Canberra is likely to rise dramatically due to the increasing need for security at the event.

Terrorism arrest

Acting Prime Minister Julia Gillard says she is concerned about possible terrorist threats to the Olympic Games but expects Australian athletes and tourists will be safe.

Ms Gillard was responding to reports from China, where police say they have arrested 45 terrorist suspects from East Turkestan and foiled plots to carry out suicide bomb attacks and kidnap athletes to disrupt the Beijing Olympics.

She told Fairfax Radio she cannot reveal the security arrangements for Australia's athletes, but she expects they will be well protected.

"I'm concerned, but in the security area we are very well assisted in this country by some great experts and professionals," she said.

Source: By Australian Broadcasting Corporation