WASHINGTON, April 20 -- Seven weeks of war have failed to topple Iran's theocratic rulers or force them to meet all of ‌President Donald Trump's demands, but for US adversaries and allies it has cast a spotlight on one of his central vulnerabilities: economic pressure. Even with Iran's announcement on Friday that it was reopening the Strait of Hormuz to shipping, the Middle East crisis has revealed the limits of Trump's willingness to tolerate domestic economic pain. Trump joined Israel in attacking Iran on February 28 based on what he said were imminent security threats, especially over its nuclear programme. But now, with US gasoline prices high, inflation rising and his approval ratings down, Trump is racing to secure a diplomati...