SINGAPORE – Singapore hopes the meeting between United States President Donald Trump and North Korean leader Kim Jong-un here will be a "first step" in reversing relations between both parties, which had been "heading in the wrong direction for some time", said Prime Minister Lee Hsien Loong.

Although longstanding tensions between both countries "cannot (be) wiped away" in just one meeting, the summit has the potential to set relations between the US and North Korea on a "new trajectory", said Mr Lee.

Speaking to the Singapore media on the sidelines of his visit to the International Media Centre at the F1 Pit building on Sunday (June 10), Mr Lee struck a moderate note when asked about outcomes expected from the summit.

"They have been at war for almost 70 years, the nuclear issue has been there for 25 years at least, since the early 1990s... There have been many discussions, agreements, broken agreements... and distrust and misunderstanding built up over many years. So you cannot wipe that all away with one meeting. What you can hope to do is to start things moving in a positive direction and hope to build up progressively along the way," he said.

"And to keep on progressing gradually until we reach a point when we can say, the nuclear problem is no longer urgent," he added.

US-North Korea relations have been hostile since the Korean war in the 1950s.

North Korea began work on a nuclear complex with the help of the Soviet Union, with both sides signing an agreement in 1959 on the peaceful use of nuclear energy.

North Korea became party to the Nuclear Nonproliferation Treaty in 1985 but withdrew in 2003.

In 2012, the US State Department announced that North Korea has agreed to a moratorium on long-range missile launches and activity at its major nuclear facility in exchange for food aid but the following year, North Korea's National Defence Commission said it would continue nuclear testing and long-range rocket launches.

The upcoming summit, the first-ever meeting between a sitting US President and a North Korean leader, will be closely watched worldwide, with many hoping it would eventually lead to nuclear disarmament.

Mr Trump himself had expressed hopes that the talks would start a process to bring about a resolution to the nuclear issue, but said that this would not be a "one-meeting deal".

Mr Lee said on Sunday: "I am hoping that it would lead to denuclearisation eventually, which will be a long process, and there (will be) many twists and turns... Whether we are hosts or not, we hope for an outcome which will set things on a constructive path."

International relations experts told TODAY Mr Lee's caution was expected.

Pointing to Pyongyang's "poor track record" in upholding pacts, S Rajaratnam School of International Studies (RSIS) research fellow Graham Ong-Webb said: "Up to eight agreements have been overturned by North Korea over the years... Of course you have to be cautious. Their track record is very poor."

Mr Lee's remarks reflect Singapore's stance as an "honest broker", said Dr Ong-Webb, who researches on geopolitics in the Asia Pacific, including weapons of mass destruction.

Agreeing, fellow RSIS researcher Tan See Seng said: "In the past, North Korea has made all sorts of promises and broken each one of them. Caution is definitely appropriate."

However, Dr Ong-Webb noted that the high stakes meeting is closely watched across the world and there are "a lot of expectations".

Associate Professor Alan Chong, who researches on international relations of Singapore and Asia, said the Republic "has very clearly a stake in the Korean peninsula".

"(Mr Lee) has put it very nicely and cautiously, and that's all that can be said at the moment... But if Pyongyang opens up to more economic co-operation with other countries, Singapore will be one of the first in line to invest in it," said Dr Chong.