“There’s an ongoing debate in Beijing between reformers who would like phase one and hard-liners who see themselves surrounded by hostile forces led by the United States, including in Hong Kong,” said Michael Pillsbury, a China scholar at the Hudson Institute who advises the Trump administration.

“There is a difference between an ambiguous stage-by-stage tariff reduction agreement versus a specific list of which tariffs will be with withdrawn for what Chinese actions,” said Michael Pillsbury, a China scholar at the Hudson Institute who advises the White House. “Neither the Chinese nor the White House has developed a specific list or a series of quid pro quo — yet. That is the next task.”

“This would be another step in ratcheting up the pressure,” said Michael Pillsbury, a China scholar at the Hudson Institute who said he raised the concept of investment restrictions with the White House after negotiations with China broke down in the spring.

“One swallow does not make a summer,” Mr. Pillsbury said, quoting a proverb. “But these gestures are now more and more numerous.”

Michael Pillsbury, a China scholar at the Hudson Institute who informally advises the White House, said that Mr. Trump had been considering more draconian options, but settled on the higher tariffs in hopes that negotiations with China would proceed.

“The U.S. government has to be careful not to do things that could be portrayed as inciting riots,” said Michael Pillsbury, a China expert at the Hudson Institute and an informal adviser to the president.