United Nations Secretary General Antonio Guterres presents his disarmament agenda at a public lecture at the University of Geneva, in Geneva, Switzerland, May 24. / EPA-Yonhap

U.N. Secretary-General Antonio Guterres said on Thursday that the parties to the North Korea talks should continue their diplomatic efforts with "nerves of steel" to work towards denuclearisation of the divided Korean peninsula.

The United Nations chief, speaking at the University of Geneva after U.S. President Donald Trump canceled next month's planned summit, said: "If I have a message to all the parties, what I ask for are nerves of steel so that one can put in place a process of dialogue capable of achieving our shared objective which must be peaceful denuclearisation and verified denuclearisation of the Korean peninsula."

A spkesman for Guterres said in a statement it was "unfortunate" that no international experts were on hand when North Korea blew up tunnels at its nuclear test site on Thursday even as he welcomed Pyongyang's reported action.

"It is regrettable that international experts were not invited to witness the site closing," the statement said. (Reuters)