A Houthi official has warned the US it would receive a “painful response” if it entered the war in Yemen, where Saudi Arabia has reportedly requested Washington’s help in dealing with the group as it weathers repeated attacks. Yemen’s civil war - in which a Saudi-led military coalition supports the government against the Iran-backed Houthis - reignited in July, months into the wider regional conflict that has roiled energy markets and plunged the Middle East into crisis. The Houthis quickly...