Geneva - Three Nobel Peace Prize-winning groups campaigning for the elimination of nuclear weapons joined forces on Monday to urge the presidents of the U.S. and Russia to meet and agree on significant denuclearization.The three groups — Japanese atomic bomb survivors' group Nihon Hidankyo, which won last year's Nobel; the International Campaign to Abolish Nuclear Weapons (ICAN), which won the prize in 2017; and the International Physicians for the Prevention of Nuclear War, the 1985 winner — have sent a joint letter to the two leaders, ICAN said in a statement Monday.'At this moment of extreme nuclear danger, we call on you to take urgent steps to de-escalate tensions and to engage in meaningful negotiations for nuclear disarmament,' they wrote to U.S. President Donald Trump and his Russian counterpart, Vladimir Putin.