Guterres urged all those concerned to "seize this momentous opportunity" and again offered UN help to achieve the goal of dismantling North Korea's nuclear weapons program.

The summit held in Singapore was "an important milestone in the advancement of sustainable peace and the complete and verifiable denuclearization on the Korean peninsula," Guterres said in a statement.

Trump and Kim signed a joint statement in which Pyongyang pledged to "work toward complete denuclearisation of the Korean peninsula" but the term "verifiable" did not appear in the text.

Agreeing to verification would entail international inspections of North Korean military sites to certify that nuclear weapons and the means to produce them have been scrapped.

Ahead of the summit, Guterres stressed that a "verifiable denuclearization" must be the "clear goal" of the summit and said experts from the International Atomic Energy Agency (IAEA) could help verify that Pyongyang's weapons program has been dismantled.

After North Korea last month invited foreign journalists to witness the closure of its Pungyye-ri nuclear test site, Guterres complained that international experts should have been there.