U.S. President Donald Trump on Monday warned that any country engaging in commercial activity with Iran would face a 25% tariff on trade conducted with the United States, as Washington considers its response to escalating unrest in Iran — the biggest anti-government protests the country has seen in years.

In a statement posted on Truth Social, Trump said:

“Effective immediately, any Country doing business with the Islamic Republic of Iran will pay a Tariff of 25% on any and all business being done with the United States of America.”

He described the order as “final and conclusive,” without offering procedural details or timelines.

Tariffs are generally paid by U.S. importers, though Trump did not clarify how the policy would be applied or enforced. Iran remains heavily sanctioned by the United States, with major export markets including China, the UAE, and India.

Notably, the White House website carried no official documentation of the policy as of Monday, nor was there any public information outlining the legal authority under which the tariffs would be imposed. The administration also did not clarify whether the measure would target all of Iran’s trading partners or only specific jurisdictions. The White House did not respond to media requests for comment.

The move comes as Iran experiences widespread unrest — its most serious challenge to clerical rule since the 1979 revolution. Protests that began over economic hardship have expanded into broader calls for political change. According to U.S.-based rights group HRANA, at least 599 people — including 510 protesters and 89 security personnel — have been confirmed dead since demonstrations began on December 28.

Tehran on Monday said communication channels with Washington remain open as Trump weighs policy responses, which have ranged from diplomatic engagement to the threat of military action. White House Press Secretary Karoline Leavitt said that “diplomacy is always the first option for the president,” while acknowledging that air strikes remain among the alternatives under consideration.

During his second term, Trump has repeatedly used tariffs as a foreign policy tool, imposing duties against countries tied to U.S. adversaries or accused of unfair trade practices. However, several of his tariff measures now face legal scrutiny as the U.S. Supreme Court reviews challenges that could potentially invalidate portions of his trade authority.

Iran, a member of OPEC, exported goods to 147 trading partners in 2022, according to World Bank data.