The measures announced by the president are unlikely to destroy the Turkish economy, as he has warned, but plenty of other existing threats could. Economists have long regarded Turkey as a bubble waiting to burst because of government mismanagement, an inflated building boom and a shaky currency. Turkey’s military incursion into Kurdish-controlled northern Syria has unsettled investors who already had concerns about the region’s stability.

Mr. Trump’s tariff threat does give investors yet another reason to be apprehensive.

“The sanctions are ineffective, and they know they are ineffective,” said Sebastien Galy, senior macro strategist at Nordea Asset Management in Luxembourg. But he added: “Tariffs frighten both businesses and consumers. They save more and invest less because they are afraid of the future. The impact on expectations can be quite considerable.”

If the president really wanted to hurt Mr. Erdogan, Mr. Galy said, he would take steps to make it difficult for Turkish commercial banks and the central bank to conduct transactions in dollars.

The White House also said Monday that it would impose sanctions on several top officials in Ankara, including the defense and energy ministers and their ministries, essentially severing them from the global financial system. Mr. Trump’s executive order allows the sanctions to be expanded to other officials or government entities.

But comprehensive financial sanctions against the Turkish government would be seen as extremely hostile considering Turkey is still nominally a NATO ally.