BEIJING — Chinese diplomats are known to be tough, but it is rare to hear descriptions of how tough. A senior Singaporean diplomat has pulled back the veil and has talked about China’s efforts to put smaller Asian countries in their place.

In a speech on Wednesday, the diplomat, Bilahari Kausikan, ambassador at large and policy adviser in Singapore’s Ministry of Foreign Affairs, who is known around Asia and in Washington for his candor, said that Chinese diplomats “perversely” often go out of their way to “accentuate rather than assuage anxieties.”

While his address, delivered at the Institute of Policy Studies at the National University of Singapore, dealt mainly with the complex power relationships among China, the United States and Southeast Asian nations, and particularly with the contentious issue of the South China Sea, Mr. Kausikan could not resist citing some examples of China’s heavy hand.

If a negotiation in Southeast Asia does not suit China, he said, its diplomats blame the other party. “It is our fault, and ours alone,” he said, explaining China’s usual attitude toward members of the Association of Southeast Asian Nations, a regional group that includes Singapore and nine other countries.