By Idrees Ali and Phil Stewart WASHINGTON (Reuters) – U.S. Defense Secretary Lloyd Austin on Monday vowed the U.S. would take “all necessary actions” to defend its troops after a deadly drone attack in Jordan by Iran-backed militants, even as President Joe Biden’s administration stressed it was not seeking a war with Iran. The attack on Sunday killed three U.S. soldiers and wounded more than 40 troops. It was the first deadly strike against U.S. troops since the Israel-Hamas war erupted in October and marks a major escalation in tensions that have engulfed the Middle East. “Let me start with m…