VATICAN CITY - The Vatican on Friday urged world leaders to shun any unilateral action and seek dialog to respond to the threat of nuclear weapons.The appeal came at the start of a two-day conference on nuclear disarmament that has brought together more than 10 Nobel prize winners, United Nations and NATO officials, discussing perspectives for a world free of nuclear weapons."Growing inter-dependence means that any response to the threat of nuclear weapons should be collective and consultative, based on mutual trust," Vatican Secretary of State Cardinal Pietro Parolin said.As tensions between the United States and North Korea have increased in recent months, Pope Francis and the Vatican have warned that a nuclear conflict would destroy a good part of humanity.US President Donald Trump, who has said North Korea "will be met with fire and fury like the world has never seen" if it threatened the United States, is visiting South Korea as part of a current trip to Asia."This trust can be built only through dialog that is truly directed to the common good and not to the protection of veiled or particular interests," said Parolin, who ranks second only to the pope in the Vatican hierarchy."Such dialog, as far as possible, should include all. Avoiding conflicts and building bridges - this should be the principle aim of an efficacious, collective and consultative response," he said.While Parolin did not mention North Korea or Trump, another participant at the conference, Cardinal Peter Turkson, said the world was in "complex and uncertain times.""By the way, when we planned this conference, we did not know that President Trump would be in the Far East. It just happens to be a happy coincidence," he added. "I guess it has to do with divine providence."During his stop in Beijing, Trump pressed China to do more to rein in North Korea's nuclear ambitions.The pope is addressing the conference later on Friday.