Trump's warning underscores persistent tensions even as Vance said in Switzerland that he hoped Washington and Tehran would "turn over a new leaf" in their relationship.
U.S. Vice President JD Vance and top Iranian officials are trying to build out the interim deal to end the war in Iran reached by the two sides last week. They are meeting at a Swiss mountainside resort near Lake Lucerne.
U.S. Vice President JD Vance landed Sunday in Switzerland to help formally launch negotiations with Iranian leaders over curbing Tehran's nuclear program and building out the fragile interim deal to end the war in Iran.
President Donald Trump continued his war of words with Italian Prime Minister Giorgia Meloni insisting she "begged" for a photo of them together despite denials.