With US President Donald Trump pledging to put American interests first, and the growing tensions in his administration, some countries in Asia have come to question whether they can still rely on the US as a global leader, Ambassador-at- Large Chan Heng Chee said yesterday.
This, coupled with China's rise, has resulted in some Asean members "entering the Chinese orbit" to greater or lesser degrees, she added.
But she said countries in the region preferred not having to choose to align themselves with one superpower over the other.
"The Asean countries really want to have good relationships with both the US and China - they really don't want to choose," she said at the FutureChina Global Forum, attended by 500 business leaders and academics.
She added that she believed there were no "zero-sum relationships in a complex world".
Professor Chan was part of a panel that was discussing relations between the United States and China at the two-day forum organised by non-profit organisation Business China.
The other panellists were Dr Shi Yinhong, director of the Renmin University of China's Centre of American Studies, and Mr Clyde Prestowitz, president of the Economic Strategy Institute.
Prof Chan noted that US policies on Asia have shown more continuity than disruption since Mr Trump took office.
She pointed out that senior members of Mr Trump's administration - Vice-President Mike Pence and Defence Secretary Jim Mattis - had also visited Asia shortly after he took office.
And while some commentators had predicted that the US and China were headed for a showdown, relations between both superpowers have stayed stable under the Trump administration, she said.
Although Mr Trump took a very hard line on China during his presidential campaign last year, he has since walked back to the "one China" policy, met Chinese President Xi Jinping and "seems to have developed a new friendship" with him, she added.
"I am just pointing all this out as evidence of more continuity than one would expect, given all the rhetoric," Prof Chan said.
During the discussion moderated by Mr Claude Smadja, president of strategic advisory firm Smadja and Smadja, the panellists also spoke of how the North Korea issue would affect US-China relations.
Dr Shi said Mr Trump was notorious for his "arrogance, volatility and lack of sense of responsibility", and seemed to view the "complicated relationship" between China and the US through the prism of the North Korea issue.
Tensions in the Korean peninsula are escalating as North Korea continues to pursue its goal of developing nuclear intercontinental ballistic missiles.
"The North Korea problem is like a type of cancer for Sino-American relations," Dr Shi said, adding that the issue has damaged ties between the two countries.
Mr Prestowitz, in response, said the US believes China has "great leverage" over North Korea, which depends economically on the Chinese.
He added that China could cut off food or fuel to get North Korea to cooperate, but "China for various reasons does not or cannot do that, and that creates a huge misunderstanding".
Prof Chan, who was Singapore's ambassador to the US from 1996 to 2012, said that her experience has led her to conclude that there are "structural elements in the US-China relationship which will not allow the relationship to go too good, nor will it go too bad".
She also noted that the duo were each other's second-largest trading partners.
But one key factor prevented strategic trust from developing between the two countries - that "deep down", the US cannot accept China's communist system of government and wants to change it, she said.
Dr Shi said both powers need to make "strategic accommodations" and respect each other's strategic interests.