Zurich: A 104-year-old Australian scientist who travelled to Switzerland to end his life has said he is not without regrets but is "happy" to have the chance.

Ecologist David Goodall, who is not terminally ill, told a news conference in Switzerland that he was ready for the end. He said he chose Switzerland as that country's liberal assisted suicide laws let him commit suicide legally, in contrast to Australia where it remains forbidden.

Professor Goodall, a member of the Order of Australia, answered reporters' questions in the Swiss city of Basel while accompanied by members of euthanasia groups including Philip Nitschke, founder of Exit International.

He understood that his death, planned for Thursday, would be by lethal injection, though he did not know what time it would take place nor many details about the procedure. Some family members would be present, he said.