SINGAPORE - The complex challenges that the world faces today are why institutions like the United Nations (UN) are more important than ever, said Prime Minister Lee Hsien Loong on Facebook.

Noting that the UN gives small states such as Singapore a voice and a stake to build peace and security in the world, PM Lee said the Republic remains committed to the open, inclusive and rules-based ideals of the UN – 57 years to the day that the city state was admitted as a member of the global body.

The 77th session of the UN General Assembly (UNGA) kicked off on Monday, with leaders of more than 150 countries attending the in-person meetings at the UN headquarters in New York for the first time in three years.

Minister for Foreign Affairs Vivian Balakrishnan is attending the UNGA until Sunday and will deliver Singapore's statement at the high-level General Debate segment.

While the world grapples with climate change, rising geopolitical tensions and growing protectionism, Covid-19 has reminded everyone how inextricably interconnected and interdependent the world is, PM Lee said on Wednesday.

"Institutions like the UN are more important than ever, providing a platform for countries to come together and build a stable international environment," he said.

Singapore's Ambassador to the UN Burhan Gafoor said in an accompanying video that the Republic has been a strong supporter of the UN and the UN Charter since its independence in 1965, with many of its diplomats having made substantial contributions to the work of the intergovernmental organisation.

"As a small country, we do have a deep interest in ensuring the success of the UN," he said.

"As a responsible member of the international community, we will continue to work closely with all countries, large and small, to find solutions to global problems."

On Wednesday, Dr Balakrishnan said he had a running start to the UNGA, having had fruitful meetings with more than a dozen leaders from various countries on Monday alone.

Besides delivering Singapore's statement at UNGA, he will participate in the Alliance of Small Island States Leaders' Meeting and the Informal Asean Ministerial Meeting, and have a series of bilateral meetings with his counterparts and with US interlocutors based in New York.

Dr Balakrishnan will also host the 15th Global Governance Group Ministerial Meeting and a reception for the Forum of Small States, which commemorates its 30th anniversary this year.