Many other countries are in a similar situation, he added during an interview with the BBC, saying they would be hard pressed if forced to pick a side.
"I hope the time does not come," he said when asked which one Singapore will choose when the time comes.
"I do not think this is a dilemma only for Singapore. It is a problem for many countries, which is why we are all hoping and encouraging the two large powers to think very carefully before deciding that the other one is an adversary which has to be kept down, if not put down."
The past few years have seen a significant deterioration in ties between the US and China, with their rivalry set to continue in spite of the change in administration in Washington.
With both sides exerting their influence on allies and partners, it has become harder for countries to stay in the middle. The administration of US President Joe Biden, for instance, has called for a review of how the country buys strategic goods, saying that it will work with like-minded countries.
Asked if it is realistic to sit on the fence in light of these developments, Mr Lee said: "I do not think we are the only ones in this boat."
He cited the European Union, which had signed an investment agreement with China before Mr Biden took office.
He also said that for Singapore, having kerfuffles from time to time, with either China or America, cannot be helped.
"Between countries, this happens. It does not mean we are your opponents, but it does mean that we have problems which need to be worked through, and meanwhile (there are) other areas where we can continue to work together. That is how we do it," he added.
Reiterating Singapore's position of assessing and making a judgment as to which course of action is in its best interests, Mr Lee said: "Generally, it is that we want to be friends with both, but we have to find our own way forward."
He also noted that competition and tension between both superpowers is inevitable in the Asia-Pacific region. But he emphasised that they have to coexist.
"These are two very major powers, neither of whom is going to be able to put the other one away, and neither of whom is going to curl up and die," he said.
Unlike the former Soviet Union which had an unsustainable economy and was pushed to the brink during the Cold War, China's economy has a lot of resilience, tremendous energy and creativity, and people who are on the move and are making great progress, he added.
The US, too, may have serious political schisms and problems, but has got tremendous vitality and attraction for people around the world, he added.
"It has come back from many difficult spots before. In that situation, unless the two powers decide to coexist, they are both in for a hard time, and so are we," he said.
Asked whether the US had to accept that it is no longer number one, Mr Lee said: "The US is still number one, but number two is not so far behind. That is what is difficult for the US to accept."
On tensions escalating, he pointed out that a real military conflict between both countries "could happen before you expect it, if there is a mishap".
"If the countries are careful, it will not happen. During the Cold War, there were many near misses, but that went on for nearly 40 years, and we avoided a nuclear catastrophe."
Mr Lee added that the odds of a military clash are not yet high, but it is more likely now than five years ago, as domestic calculations have become paramount for both sides.
"It is not so easy to say the external logic compels you to work together, because the internal logic may impel you to take a very hard line, and then you may find yourself at an impasse and clash. That can easily happen," he added.
Asked what he hoped the US and China would do, Mr Lee said he would hesitate to give advice to other countries' leaders.
On President Biden, he added: "We look to a President who has first, good domestic support. Second, a good understanding of the world and the US' role in the world, believes in multilateralism and international trade, and is prepared to play America's part to uphold the system from which America benefits so much."
As for China, he said: "What we would like to see is China being able to be a country where its prosperity, development and its growing strength is welcomed by other countries in the world, who see this as an opportunity for them to prosper together and to live in a stable world together."
This has been the case for quite a long time, he added, noting how over the last 40 years since its opening up, China's liberalisation and growth have generated many opportunities for countries around the world, who want very much to maintain good relations with it in order to benefit from its development and prosper together with it.
"That is a very important factor which China has had in its favour, which would be a pity to miss out on in the next phase," he added.
Mr Lee also noted that American businesses like Walmart were one of the strongest advocates for good relations with China, because they saw the opportunities it offered.
But attitudes have shifted in the last five to seven years and there is quite a lot of pushback, as these businesses see China has moved forward. They want to see a more open environment, where they get a bigger bite of the cherry, he added.
"It is understandable. China is in a new position now, and you have to set a different balance in your relationship with the world," he added.
"What the world was prepared to grant you in an earlier phase now has to be reworked, and that is quite difficult for a country to accept."
Published : March 15, 2021
By : Tham Yuen-C The Straits Times/ANN