President Donald Trump threatened Monday to impose a 25 percent tariff on “any country” doing business with Iran, potentially affecting U.S. trade with China, India, the United Arab Emirates, the European Union and others.

“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 a post on Truth Social. “This Order is final and conclusive. Thank you for your attention to this matter!”

However, Trump does not appear to have issued an executive order to back up his statement as of late Monday afternoon. A White House spokesperson also did not immediately respond to questions about Trump’s social media post.

The threat follows reports from human rights groups that hundreds of people have been killed in a brutal crackdown on protests against the Iranian regime that intensified over the weekend. Trump has previously warned that the U.S. could intervene if Iran’s government uses violence against the protesters.

“For President Trump this seems like a pretty mild response to a very significant situation in Iran and so this will probably disappoint many in the Iranian American community,” said Michael Singh, former senior director for Middle East affairs at the National Security Council under President George W. Bush, now the managing director at the Washington Institute for Near East Policy. “The problem is that we have sanctions in place against Iran that are quite tough, but they’re not being enforced — I mean Iran is selling lots of oil, and so I think the question will be what’s new here and is it going to be enforced, unlike the other sanctions that are already in place.”

The U.S. has little direct trade with Iran because of its steep sanctions on the country, imposed in recent decades to punish Tehran for its nuclear program. Last year, it imported just $6.2 million worth of goods from the country and exported slightly more than $90 million worth of goods to Iran in return, according to Commerce Department statistics.

However, the United States does substantial trade with countries that do business with Iran, including China, India, the United Arab Emirates and the EU.

Earlier this year, Trump threatened to impose tariffs on any country that buys Russian oil but so far has only taken that action against India, sparing China in the process. He also threatened in March to impose a 25 percent tariff on any country that buys oil or gas from Venezuela, but doesn’t appear to have followed through on that threat.

Phelim Kine contributed to this report.