President Donald Trump on Thursday said any country purchasing oil from Iran will be barred from doing business with the U.S., with the threat of “secondary sanctions” coming amid a bubbling trade war and negotiations over Iran’s nuclear program. Trump’s threat is an escalation against both Iran and China — the world’s largest importer of Iranian oil. “ALERT: All purchases of Iranian Oil, or Petrochemical products, must stop, NOW! Any Country or person who buys ANY AMOUNT of OIL or PETROCHEMICALS from Iran will be subject to, immediately, Secondary Sanctions,” the president said in a post on Truth Social. “They will not be allowed to do business with the United States of America in any way, shape, or form.”

President Donald Trump on Thursday threatened sanctions on anyone who buys Iranian oil, a warning that came after planned talks over Tehran’s rapidly advancing nuclear program were postponed. Trump wrote on social media, “All purchases of Iranian Oil, or Petrochemical products, must stop, NOW!” He said any country or person who buys those products from Iran will not be able to do business with the United States “in any way, shape, or form.” It was unclear how Trump would implement such a ban as he threatened to levy secondary sanctions on nations that import Iranian oil. But his statement risked further escalating tensions with China — Iran’s leading customer — at a time when the relationship is severely strained over the U.S. president’s tariffs.

Despite being in active nuclear negotiations with the Iranian regime, Trump has kept up his “maximum pressure” campaign on Iran to prevent it from obtaining a nuclear weapon and curb its backing of terror organizations across the Middle East. If negotiations fail, the president has repeatedly warned that military action remains on the table to disrupt Iran’s nuclear ambitions.