The United States will not hesitate to act to protect its personnel in Iraq, where it considers Iranian-backed militias that have attacked U.S. targets to be the country’s “single biggest problem,” a senior State Department official said on Thursday. David Schenker, Assistant Secretary of State for Near Eastern Affairs, issued the warning when asked during a briefing about U.S. threats to close its embassy in Baghdad. He declined to comment on what he called Secretary of State Mike Pompeo’s “private diplomatic conversations” but added, “We can’t tolerate the threats to our people, our men and women serving abroad.”