A rules-based multilateral system, with the United Nations at its core, is the world's best hope to build a stable environment that can respond effectively to global challenges, Singapore Prime Minister Lee Hsien Loong has said.

"For all its limitations, it has helped to level the playing field for all countries," PM Lee said of the UN in a video recording for the High-Level Meeting to commemorate its 75th anniversary yesterday (this morning, Singapore time).

In his remarks, PM Lee called on members to work together to update and reform multilateral institutions like the UN so that they can remain open, inclusive, and able to respond effectively to shared challenges - including pandemics and climate change.

The UN has given small states like Singapore a voice and a stake in the global commons, he said.

Major powers also benefit from a more peaceful and stable global environment, and when they take joint initiatives through multilateral institutions, it enhances their political legitimacy and moral authority, he added.

As the UN commemorates a milestone year, its meetings, including the upcoming General Assembly, are almost completely virtual. The pandemic and quarantine restrictions have made it impractical or impossible for most world leaders to travel to New York City this month.

But up to 170 world leaders were expected to deliver video addresses for the anniversary meeting, which has as its theme "The future we want, the United Nations we need", with a strong focus on the role of youth and ensuring the UN - which has 193 member states - remains relevant for future generations.

In his message, PM Lee highlighted that Covid-19 is a reminder of how interconnected and interdependent countries are, and the need for international cooperation to overcome the pandemic.

"The world was changing even before Covid-19," he said. "Geopolitical tensions were growing; globalisation was showing fissures; isolationism, protectionism and unilateralism were pushing back against multilateral institutions and international cooperation. The Covid-19 crisis has sharpened these trends, but it has also reminded us how interconnected and interdependent countries are, and why we all need to work together to defeat the gravest challenge of our time."

PM Lee acknowledged that recent trends have exposed multilateral institutions' shortcomings - the inability to achieve consensus on major issues, the conflicts that continue to ravage societies, and the millions who still lack access to food, healthcare and education.

"We must work together to update and reform our multilateral institutions - including the UN - to keep the institutions open, inclusive, and fit for purpose, to reflect current economic and political realities, and to respond effectively to shared challenges of our time, including pandemics, climate change, extremist terrorism, sustainable development and cyber security," he said.

PM Lee had addressed the UN in person at the General Assembly last year, when he said that a rules-based system imposes responsibilities on all countries and creates a stable environment for all.

In his message this year, he noted that member states expect a lot from the organisation.

"It is only right that we give the UN commensurate latitude, resources and mandate to fulfil its demanding mission," he urged.

He noted that when Singapore was admitted to the UN in 1965, its first foreign minister S. Rajaratnam said: "Despite the cynics who focus attention on its many shortcomings, my country has faith in the future of the United Nations, simply because without it there is no worthwhile future for humanity."

That statement holds true today, PM Lee said.

"Singapore is committed to the future of the UN, and the values and ideals of the UN Charter," he added.

"We are equally determined to work with all countries, including through the Forum of Small States which we helped to establish, to strengthen the UN."

Singapore founded the forum in 1992 as an informal grouping for nations with populations under 10 million to discuss issues of common interest. It now has 108 members.