U.S. military officials are accusing the highest levels of the Iranian government of sending sophisticated roadside bombs to Iraq that have killed 170 coalition troops since 2004. On Sunday, reporters in Baghdad received an unusual briefing on the allegations. The news conference was led by three U.S. military officials who refused to be quoted by name. No TV cameras or tapes were allowed in, and journalists’ cellphones were taken away before they entered the briefing room. Iran is denying the charges. One Iranian official said, “We ask those who are claiming such evidence: Show the documents in public.” The bomb allegations first appeared on Saturday in a front-page article written by Michael Gordon titled “Deadliest Bomb in Iraq Is Made by Iran, US Says.” The article relied almost entirely on unnamed government sources. Several media critics compared the piece to Gordon’s articles from 2002 alleging Iraq had weapons of mass destruction.