“The existence of zero nuclear weapons may sound utopian, but the effort is required in the name of humanity.”

"Reaching Global Zero" (8 March 2011) http://www.huffingtonpost.com/valerie-plame-wilson/nuclear-proliferation_b_832399.html
Context: Without doubt, terrorist groups are trying to buy, build or steal a bomb. Furthermore, there is enough highly-enriched uranium (HEU) in the world to build more than 100,000 weapons, and rogue individuals are selling technology on the black market. If terrorists get hold of HEU, they could not be prevented from smuggling it into a targeted city, building a bomb and exploding it.
To my mind, the only realistic solution to this danger is to lock down all nuclear materials and eliminate all nuclear weapons in all countries: Global Zero. I am now dedicated to achieving this goal as a leader of the Global Zero movement. This movement was launched in December 2008 in Paris by an international group of 100 current and former heads-of-state, national security officials, military commanders and business, civic and faith leaders — and in just two years has grown to 300 leaders and 400,000 citizens worldwide.
The group believes that whatever deterrent value nuclear weapons had in the Cold War is now outweighed by the dangers of proliferation and nuclear terrorism. Our international Global Zero Commission has developed a practical, step-by-step plan to eliminate all nuclear weapons through phased and verified reductions.
To build on the progress made to date, we need a worldwide public movement to make Global Zero an urgent global imperative — and to bring all nuclear weapons countries to the table to negotiate multilateral nuclear arms reductions for the first time in history.

Quoted in https://www.bbc.com/news/av/world-europe-50265870/mikhail-gorbachev-tells-the-bbc-world-in-colossal-danger Mikhail Gorbachev tells the BBC: World in ‘colossal danger’, BBC World News,(4 November 2019)
2000s

"Introduction: Thinkability"
Einstein's Monsters (1987)

Speech at a Soviet Official banquet http://www.margaretthatcher.org/speeches/displaydocument.asp?docid=106776, St George's Halls, the Kremlin (30 March 1987)
Second term as Prime Minister

Debunking the view of the left wing of the 1980s New Zealand Labour Party that the Lange Government's nuclear weapons ban should also extend to nuclear propulsion.
Source: David Lange, My Life (2005).

"Reaching Global Zero" (8 March 2011) http://www.huffingtonpost.com/valerie-plame-wilson/nuclear-proliferation_b_832399.html
Context: Without doubt, terrorist groups are trying to buy, build or steal a bomb. Furthermore, there is enough highly-enriched uranium (HEU) in the world to build more than 100,000 weapons, and rogue individuals are selling technology on the black market. If terrorists get hold of HEU, they could not be prevented from smuggling it into a targeted city, building a bomb and exploding it.
To my mind, the only realistic solution to this danger is to lock down all nuclear materials and eliminate all nuclear weapons in all countries: Global Zero. I am now dedicated to achieving this goal as a leader of the Global Zero movement. This movement was launched in December 2008 in Paris by an international group of 100 current and former heads-of-state, national security officials, military commanders and business, civic and faith leaders — and in just two years has grown to 300 leaders and 400,000 citizens worldwide.
The group believes that whatever deterrent value nuclear weapons had in the Cold War is now outweighed by the dangers of proliferation and nuclear terrorism. Our international Global Zero Commission has developed a practical, step-by-step plan to eliminate all nuclear weapons through phased and verified reductions.
To build on the progress made to date, we need a worldwide public movement to make Global Zero an urgent global imperative — and to bring all nuclear weapons countries to the table to negotiate multilateral nuclear arms reductions for the first time in history.

Nobel Peace prize acceptance speech (1985)
Context: I am convinced that today is a great and exciting day not only for the members of our international movement but also for all physicians on our planet, irrespective of their political and religious beliefs. For the first time in history, their selfless service for the cause of maintaining life on Earth is marked by the high Nobel Prize. True to the Hippocratic Oath, we cannot keep silent knowing what final epidemic-nuclear war — can bring to humankind. The bell of Hiroshima rings in our hearts not as a funeral knell, but as an alarm bell calling out to actions to protect life on our planet.
We were among the first to demolish the nuclear illusions that existed and to unveil the true face of nuclear weapons — the weapons of genocide. We warned the peoples and governments that medicine would be helpless to offer even minimal relief to the hundreds of millions of victims of nuclear war.
However, our contacts with patients inspire our faith in the human reason. Peoples are heedful of the voice of physicians who warn them of the danger and recommend the means of prevention.

On potentials for misuse of nuclear power, p. 31
Portraits in Science interviews (1994)
Context: I, who had been in favour of nuclear energy for generating electricity … I suddenly realised that anybody who has a nuclear reactor can extract the plutonium from the reactor and make nuclear weapons, so that a country which has a nuclear reactor can, at any moment that it wants to, become a nuclear weapons power. And I, right from the beginning, have been terribly worried by the existence of nuclear weapons and very much against their use.

Progress, Coexistence and Intellectual Freedom (1968), Dangers, The Threat of Nuclear War