The COVID-19 caught the world off guard, which is a reminder for all nations of improving their preparedness for various challenges and crises by strengthening international cooperation, coordination and solidarity, says the UN.

NEW YORK, Sept. 21 -- The world's challenges are interconnected and can only be addressed through reinvigorated multilateralism, which is a necessity as we build back better for a more equal, more resilient and more sustainable world, the United Nations (UN) said Monday in a declaration to commemorate its 75th anniversary.

Volkan Bozkir (rear L), president of the 75th session of the United Nations General Assembly (UNGA), addresses a high-level meeting to commemorate the 75th anniversary of the UN at the UN headquarters in New York, on Sept. 21, 2020. (Eskinder Debebe/UN Photo/Handout via Xinhua)

The COVID-19 pandemic, the largest global challenge in the history of the UN, has not only caused death and serious illness, but also global economic recession, increased poverty, anxiety and fear, leaving no one untouched, the UN said.

"The COVID-19 pandemic has reminded us in the most powerful way that we are closely interconnected and only as strong as our weakest link," the UN noted, calling for solidarity to end the pandemic and build resilience against future challenges.

Thus, multilateralism has become a "necessity" as the world has been striving to "build back better for a more equal, more resilient and more sustainable world," it said, stressing that the UN must be at the center of these efforts.