In the span of about eight hours, President Donald Trump went from suggesting a nuclear deal with Iran remained “achievable” to urging Tehran’s 9.5 million residents to flee for their lives as he cut his visit to the international G7 summit short to return to Washington for urgent talks with his national security team.

Tehran, home to 10 million people, suffers from severe traffic congestion making a speedy evacuation impossible.

President Donald Trump urged civilians living in Tehran to evacuate the Iranian capital "before there is nothing left."