The 104-year-old Australian scientist who has chosen to end his life at a Swiss clinic says he would have preferred to have done so in Australia.
"Australia is behind Switzerland in this move, as are most countries," Professor David Goodall said at a final press conference in the Swiss city of Basel on Wednesday.
He was accompanied by Dr Philip Nitschke, founder of Australian right-to-die group Exit International, and Swiss clinic Life Circle's lawyer Moritz Gall.
"At my age, or less than my age, one wants to be free to choose the death when the death is at an appropriate time," Prof Goodall said.
"My abilities have been in decline over the past year or two, my eyesight over the past six years. I no longer want to continue life. I'm happy to have the chance tomorrow to end it."
Prof Goodall flew from his home in Western Australia, where his daughter, son and grandchildren also live, to France last week to see relatives before arriving in Switzerland.
"Luckily my family who are in various parts of Europe and America have rallied round and come to see me, and I welcome the opportunity to see them, which I probably wouldn't have had if I hadn't pursued this Swiss option."
Prof Goodall was cleared by two Swiss doctors, including a psychiatrist on Wednesday who said he was of sound mind, to proceed with the "Swiss option".
The esteemed botanist and ecologist, who does not believe in the afterlife and has been a member of Exit International for 20 years, said he tried clumsily to take own his life at least three times, and then finally decided to get professional help.
He hopes to his story will help countries like Australia change their laws to be more accepting of assisted suicide.
"I certainly hope my story will increase the pressure for people to have more liberal view on the subject [of voluntary euthanasia]," he said. "I think there probably will be a step in the right direction."
Victoria was the first state to pass a euthanasia bill last November but it doesn't become legal until the middle of 2019.
Prof Goodall will make his final journey on Thursday local time in the presence of family members.
Readers seeking support and information about suicide prevention can contact Lifeline on 13 11 14.
Suicide Call Back Service 1300 659 467.