WASHINGTON, April 8 - U.S. President Donald Trump said on Wednesday that imports from countries supplying Iran with military weapons will face immediate 50% tariffs with no exemptions, announcing the threatened duty in a social media post just hours after agreeing to a two-week ceasefire with Tehran.

Trump's Truth Social post did not specify which legal authority he would invoke to impose such tariffs, as the Supreme Court in February struck down his use of the International Emergency Economic Powers Act to impose broad global tariffs, prompting a lower court to order refunds of some $166 billion collected over the course of a year.

The 1977 IEEPA law has been used extensively for decades to back financial sanctions against Iran, Russia and North Korea, but the court ruled that Trump overstepped his authority in using it to impose trade tariffs.

"A Country supplying Military Weapons to Iran will be immediately tariffed, on any and all goods sold to the United States of America, 50%, effective immediately, There will be no exclusions or exemptions! President DJT," Trump wrote.

He did not name any countries that could face punitive tariffs. China and Russia have helped Iran build military capacity to counter U.S. and Israeli pressure, supplying missiles, air-defense systems and technology intended to bolster deterrence.

But that support appeared capped during the U.S.-Israeli attacks on Iran. Both Beijing and Moscow have denied supplying any weapons recently, although allegations against Moscow have persisted.

Reuters reported in February, prior to the first U.S. and Israeli strikes on Iran, that Tehran was considering a purchase of supersonic anti-ship cruise missiles from China. Reuters also reported in March that China's top semiconductor maker, SMIC , has sent chipmaking tools to Iran's military, according to two senior Trump administration officials.

ALTERNATIVE TARIFF TOOLS

Trump does have active "Section 301" unfair trade practices tariffs on Chinese goods from his first term to which he may be able to add duties and similar pending cases relat...