JEJU, South Korea, June 25 (Xinhua) -- UN Secretary-General Antonio Guterres warned on Thursday that multilateralism is facing severe challenges, calling for stronger cooperation and renewed trust to tackle global challenges, including conflicts, poverty and climate change.

In a video message to the 21st Jeju Forum for Peace and Prosperity, he urged countries to reaffirm their commitment to the UN Charter and shared values.

In his address at the forum, former UN Secretary-General Ban Ki-moon expressed concern over the weakening influence of the United Nations and other international institutions.

"What makes me particularly angry is that U.S. President Donald Trump decided to withdraw the United States from a large number of UN-related and international organizations," Ban said.

Ban stressed that no country, regardless of its power and resources, can thrive in isolation.

Also speaking at the forum, former Japanese Prime Minister Yukio Hatoyama criticized the recent military actions against Iran by the United States and Israel, saying they had "clearly violated international law."

The Jeju Forum was launched in 2001 under the theme of peace and prosperity. ■