The move introduces considerable uncertainty for major economies that maintain trade relations with Iran, including Russia, China, Brazil, and Turkiye. The potential impact on global markets is substantial, with analysts predicting volatility in sectors ranging from energy to manufacturing. A 25 percent tariff could significantly increase the cost of goods imported from countries trading with Iran, potentially leading to inflationary pressures in the U.S. and retaliatory measures from affected nations.

"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," Trump wrote in his post.

The Trump administration has consistently pursued a policy of maximum pressure on Iran, withdrawing from the 2015 nuclear deal and reimposing sanctions aimed at curbing Iran's nuclear program and regional influence. This latest measure appears to be a further attempt to isolate Iran economically and compel it to renegotiate a new agreement.

The announcement comes amid ongoing protests in Iran and heightened tensions in the Middle East. The U.S. administration has stated it is considering various options regarding Iran, including potential military action.

The implications for specific companies remain unclear, but businesses with significant exposure to both the U.S. and Iranian markets face difficult choices. Companies may be forced to choose between maintaining access to the U.S. market and continuing trade with Iran, potentially leading to significant financial losses. The U.S. Trade Representative's office is expected to release further guidance on the implementation of the tariff in the coming days, which will provide more clarity on the scope and enforcement of the new policy.