Fourth U.S.-Iran nuclear talks stall; Trump calls Iran counteroffer 'totally unacceptable'

The fourth round of U.S.-Iran nuclear talks in Oman on May 11 lasted more than three hours but ended without a breakthrough, with both sides calling it difficult but constructive. Trump dismissed Iran's ceasefire counterproposal as totally unacceptable, and on May 12 the U.S. imposed new sanctions targeting Iranian nuclear research.