“Everyone should be calm and safe!” he added.

Critics and allies alike said that the combination of Mr. Trump’s relative disinterest in human rights and his narrow focus on America’s economic relationship with China leave him with little appetite for taking sides in the escalating showdown between China’s government and the protesters in Hong Kong. But some warned that he was tacitly approving what many fear could be the most brutal suppression of democratic dissent in China in nearly 30 years.

In his comments to reporters, Mr. Trump did allow that he “hopes it works out for liberty,” without explaining what he meant. He did not offer any opinions about the protesters’ demands for more political freedom and protection from mainland China’s growing influence in the former British colony.

This month, Mr. Trump echoed Chinese state media by calling the demonstrations “riots” and said, “That’s between Hong Kong and that’s between China, because Hong Kong is a part of China.”

Democrats have been sharply critical of Mr. Trump, painting him as weak and equivocal in the face of a threat to fundamental American values.

“This is not foreign policy,” Senator Christopher S. Murphy, Democrat of Connecticut, responded on Twitter to Mr. Trump’s tweets. On Monday, Senator Elizabeth Warren, a Massachusetts Democrat who is running for president, tweeted that the people of Hong Kong “deserve our support and the support of the world.”