The Dalai Lama and other Nobel Peace laureates ended a Hiroshima meeting Sunday by calling for a nuclear-free world but made no statement on this year's winner, Chinese dissident Liu Xiaobo.

The failure to mention Liu sparked discord at the annual World Summit of Nobel Peace Laureates, which had earlier greeted Saturday's release from house arrest of another winner, Myanmar's democracy leader Aung San Suu Kyi.

"I feel I need to say something," the 1997 winner Jody Williams said at a joint news conference of the laureates, including the exiled Tibetan spiritual leader and former South African president F.W. de Klerk.

"We also have to recognise another," said Williams of the International Campaign to Ban Landmines. "One of our Nobel Peace colleagues is imprisoned."

"We cannot be silent in the face of pressure from the Chinese government."

"Liu Xiaobo is not forgotten. We will work as diligently for his release as we have for that of our sister Aung San Suu Kyi."

Former Chinese student leader Wu'er Kaixi, who was involved in the 1989 Tiananmen Square protests, joined the summit of six Nobel winners and earlier urged China to "release Liu Xiaobo immediately and unconditionally".

The Dalai Lama welcomed the choice of Liu for the prize.

An organising source said the laureates had earlier approved a draft statement on Liu, but decided not to release it "out of respect" for the host city's position, which wanted to keep the focus on nuclear weapons.

De Klerk, who shared the 1993 prize with Nelson Mandela, said "the main focus of this conference was on the abolition of nuclear arms and we didn't want to take the spotlight away from the main issue."

Asked at the press conference if there had been any pressure to drop a statement on Liu, de Klerk said: "To the best of my knowledge, none of us have been pressurised in any way or anybody."

The Nobel laureates, after meeting for three days in the city destroyed in the world's first atomic bombing in 1945, on Sunday issued their Hiroshima Declaration on the Abolition of Nuclear Weapons.

"Nuclear deterrence, power projection and national prestige as arguments to justify acquiring and retaining nuclear weapons are totally outdated and must be rejected," the declaration said.

The United States dropped an atomic bomb over Hiroshima on August 6, 1945, and an estimated 140,000 people died instantly in the city or succumbed to burns and radiation sickness by the end of the year.

More than 70,000 people perished as a result of the second US atomic bombing of the port of Nagasaki three days later.

The Nobel winners had invited US President Barack Obama -- who was in Japan for an Asia-Pacific summit -- after he won the Nobel Peace Prize in 2009, in part for his call for a world free of nuclear weapons.

Hiroshima city earlier voiced its disappointment about the no-show by Obama, who has said in the past that he would like to visit Hiroshima and this year for the first time sent the US ambassador, John Roos, to join the commemoration ceremony on the 65th anniversary of the attack.

No sitting US president has ever travelled to Hiroshima or Nagasaki.