Chairmen of the conference’s advisory board include Henry A. Kissinger, the former secretary of state and national security adviser, and Henry M. Paulson Jr., the former Treasury secretary, both of whom occasionally meet with Chinese leaders and preach engagement with China. Among the international corporate partners are ExxonMobil, HSBC and SoftBank Group, based in Japan.

The Chinese partner, the China Center for Economic International Exchanges, is a research center based in Beijing that is led by Zeng Peiyan, a former vice premier. Its mission, according to the center’s website, includes “promoting exchanges and cooperation” and “to improve China’s soft power.”

The group did not respond to phone calls and emails seeking comment.

Its request last week came as a blow to Mr. Bloomberg, who wants to engage with China on issues such as trade and climate change.

Organizers scrambled to find another site, and prominent Singaporeans agreed to host, the people familiar with planning said. The Chinese center is still expected to send some participants, but there will now be less of a focus on China, and programmers are scrambling to line up speakers after some dropped out, the people said.

“I think it’s more clear that the increasing tensions in the U.S.-China relationship are having an impact on everything,” said Scott Mulhauser, the former chief of staff to Max Baucus, an ambassador to China under the Obama administration, and founder of Aperture Strategies, a public relations firm. “I think Bloomberg navigated this one impressively. It’s not clear that everyone can.”

The strengthening of authoritarianism in China poses a dilemma for Westerners who want to engage with the country but also say that they champion liberal thought and freedoms, as Mr. Bloomberg does.

In that context, some experts say, the move to Singapore could benefit the event.

“It’s almost impossible to do anything in China that’s meaningful,” said Orville Schell, the director of the Center on U.S.-China Relations at the Asia Society, who has organized events in China. “As much as we see a need to have frank and honest discussions, it’s almost impossible to confect such a thing in China. In my opinion, Singapore is a much better choice.”