The Dalai Lama has called for a denuclearised world and warned force would not solve the North Korean crisis.
Leaders are not using common sense, the Tibetan spiritual leader added, amid heightened tensions and military exercises.
He called for a century of peace.
"We must seriously make efforts, step-by-step, for a nuclear-free world," he said.
The Dalai Lama visited Londonderry in Northern Ireland for a charity event.
His intervention followed deepening tensions on the Korean Peninsula as Pyongyang steps up nuclear tests.
North Korea's nuclear weapons programme must be halted before it develops a ballistic missile capable of hitting London, according to the Defence Secretary.
Sir Michael Fallon has said war must be avoided "at all costs" and stressed the desire for a diplomatic solution, given that the dangers of a "miscalculation" triggering a military response against North Korea are "extremely great".
The United States is seeking a vote on a United Nations resolution which would impose the toughest-ever sanctions on North Korea.
The Dalai Lama said the emphasis should be placed on talks.
"To show force, I think, cannot solve the problem.
"Using this force will cause tremendous suffering, particularly South Korea, then to some extent I think Japan also.
"Unthinkable to use nuclear weapon, unthinkable, now we must seriously make effort step by step, for a nuclear-free world.
"Then eventually the weapons, I think this world should be a demilitarised world."
The 82-year-old said it would not be achieved within his lifetime.
"But it is our duty (to make) efforts to achieve (a) demilitarised world.
"A century of dialogue."
He called on US President Donald Trump to pay more attention to ecology.
The Dalai Lama said he was saddened by the US leaving the Paris climate accord.
"America, the most industrialised nation and the leading nation of free world, should take more active responsibility regarding ecology."