“They’re going to go after the Central Bank of China just before the midterms?” said Daniel Fried, a top White House and State Department official in the administration of President George W. Bush. “The next day’s headline will be: ‘Dow Drops 5,000 Points.’”

Peter Harrell, a former sanctions official in the State Department, dismissed the idea outright. “I don’t see China and India going to zero,” he said.

Next week’s meeting in Vienna will come just two days after President Hassan Rouhani of Iran is expected to visit the Austrian capital to discuss the nuclear deal.

This month, European leaders applied for waivers to the renewed American sanctions against Iran, saying that preserving the agreement was vital to the security of their respective nations. Few expected the waivers to be granted, but Tuesday’s abrupt announcement, which largely ruled them out, could cause further strains.

Briefing reporters on condition of anonymity, a top State Department official said that he had yet to visit India or China to discuss the re-imposition of sanctions.

But he said that companies in both countries that continue to buy oil and other products from Iran after Nov. 4 will be barred from selling anything in the United States. The official acknowledged that other nations rarely want to voluntarily end imports but do so to preserve their relationships with the United States.

European diplomats spent months negotiating a side agreement to the Iran deal with Brian Hook, a top State Department official, hoping such an agreement would persuade Mr. Trump to stay in the accord. In April, President Emmanuel Macron of France told Mr. Trump in the Oval Office that negotiations with Mr. Hook were about to yield a strong agreement. “Who’s Brian Hook?” Mr. Trump responded, according to a person with knowledge of the exchange.