GENEVA -- South Korea's top diplomat said Monday that an end to North Korea's nuclear and missile tests would be good, but "just the beginning," after U.S. President Donald Trump said he would be "happy" as long as no testing takes place.

Foreign Minister Kang Kyung-wha said South Korea hopes for tangible results from this week's summit between Trump and North Korean leader Kim Jong Un in Hanoi, Vietnam.

Kang said she was hopeful for "a substantial outcome" on issues of denuclearization and "corresponding measures from the United States."

The comments came after Trump said Sunday he was in no hurry for North Korea to prove it was abandoning its weapons, adding: "I just don't want testing. As long as there's no testing, we're happy."

Speaking to the UN-backed Conference on Disarmament in Geneva, Kang insisted complete denuclearization "requires many more concrete steps."

UN Secretary-General Antonio Guterres later told the 65-member body that he hoped the U.S. and North Korean leaders would agree on "concrete steps for sustainable, peaceful, and complete and verifiable denuclearization of the Korean Peninsula."