Three European powers met with an Iranian minister to try to reopen negotiations over the limits of its nuclear activities.

U.S. President Donald Trump expressed frustration with Iran’s leadership on Sunday, telling reporters on the sidelines of a meeting with the European Commission that Tehran doesn’t seem to comprehend the scale of the damage done to its nuclear program.

Trump issued the threat as he held talks with British Prime Minister Keir Starmer at his Turnberry golf resort on the western coast of Scotland.