BANGKOK - With the global economy facing strengthening headwinds, and as support for multilateralism weakens, it has become ever more important for Asean nations to work closely to meet these challenges, said Prime Minister Lee Hsien Loong on Saturday.

"Each Asean member state has our own domestic preoccupations," he said.

"But this global backdrop has made it more urgent than ever for Asean to come together, to deepen cooperation among ourselves, in order to counter these unfavourable external trends, and to speak on the issues that concern us with one voice."

Addressing fellow leaders of South-east Asian nations at the start of the 35th Asean Summit, PM Lee noted that the global economy is forecast to grow by 3 per cent this year, the slowest since the global financial crisis a decade ago. The risk of a US recession is also on the rise.

At the same time, populism is gaining ground around the world, leading to a weakening of support for globalisation and multilateralism.

With this as backdrop, PM Lee touched on three areas that the 10-member bloc had to tackle together - the economy, the environment, and security.

On the economic front, PM Lee said Asean needed to intensify its efforts to uphold a free, open and rules-based multilateral trading system.

"Internally, we have established the Asean Community in 2015, now, we should take the next step, to fully implement the Asean Economic Blueprint 2025, in order to complete the unfinished agenda," he said.

"Externally, we should widen our economic links with Asean's partners, and further liberalise trade with them."

He noted that as Asean works towards advancing negotiations on the Regional Comprehensive Economic Partnership (RCEP), it could also concurrently explore new areas for economic cooperation.

One example is the Asean Smart Cities Network (ASCN), which was launched last yearto facilitate member states to share information and explore funding for smart city initiatives.

"The ASCN will enhance Asean's proposition as a single digital market and generate new growth for our countries," he said. "As the ASCN Shepherd, Singapore will work with member states to develop the network further, including of course with the next chairman, Vietnam."

On the environment, PM Lee said that Singapore supports multilateral solutions to challenges like climate change, and transboundary pollution, such as haze pollution. He urged Asean states to fully implement its agreement on transboundary haze pollution so they can deal with the problem more effectively.

In order to meet the challenges of economic and environmental changes, peace and security in the region was vital, he said, as he welcomed progress made in agreeing a code of conduct in the South China Sea.

Asean and China have completed the first reading of the Single Draft Negotiating Text for a South China Sea Code of Conduct (COC), and he said that as Asean moves forward in the negotiations, it should continue to reiterate its shared principles of respect for the freedom of navigation and overflight, self-restraint including non-militarisation, and peaceful resolution of disputes in accordance with international law.

PM Lee also raised concerns about the situation in Myanmar's Rakhine State, calling it a "complex problem with both humanitarian and security dimensions".

Over 700,000 Rohingya refugees from Rakhine State fled to Bangladesh to seek refuge following a military crackdown in 2017.

"Asean should continue to support efforts by all parties, including the Myanmar government, to work towards a comprehensive and durable solution," he said.

"Commencement of repatriation on a safe, voluntary, and dignified basis should remain an immediate priority."

PM Lee and other Asean leaders are scheduled to hold discussions with key partners like China, Japan, India and the United States during the summit, which ends on Monday.