“Today, I myself am even closer to the departures hall than arrivals, so to speak, and my thoughts turn to how I would like to be treated when the time comes,” Tutu wrote in an op-ed published in The Washington Post.
“I have prepared for my death and have made it clear that I do not wish to be kept alive at all costs,” said Tutu, who was discharged from hospital late last month.
“I hope I am treated with compassion and allowed to pass on to the next phase of life’s journey in the manner of my choice,” he wrote.
Tutu, who is fondly referred to as the Arch, has spent time in hospital on several occasions since last year for a nagging infection.
One reason for his hospitalisation has been an infection resulting from the prostate cancer treatment he has been receiving for nearly 20 years.
“Now more than ever, I feel compelled to lend my voice to this cause,” he said.
“For those suffering unbearably and coming to the end of their lives, merely knowing that an assisted death is open to them can provide immeasurable comfort.”
Medically-assisted suicide or voluntary euthanasia is illegal in South Africa, but in recent years there have been growing calls for it to be legalised.
He paid a moving tribute to St George’s Cathedral before laying his head on the communion table and briefly wept.
“I have indicated that when the time comes I would like to rest here, permanently, with you,” he told the worshippers.
Tutu, who became the first black Anglican archbishop of Cape Town in 1986, had a cup of tea with worshippers after the Friday morning service.
President Jacob Zuma and the last apartheid leader F.W. de Klerk led tributes to Tutu.
In a statement Zuma said Tutu “has contributed immensely to the freedom and democratic dispensation” of South Africa.
“He continues to inspire the nation and the world in the promotion of human rights, justice and the wellbeing of all especially the poor,” said Zuma.
De Klerk and his foundation wished Tutu “the best of health in the year ahead,” and acknowledged “his valuable role as a peacemaker, as well as his contribution towards goodwill between all South Africans, and towards South Africa’s constitutional democracy.”
Ordained at the age of 30 and appointed archbishop in 1986, Tutu used his position to advocate for international sanctions against white-minority rule in South Africa, and later to lobby for rights globally.
He won the Nobel Peace Prize in 1984.