Should Israel attack Iran, a larger regional war in the Middle East could erupt, drawing in the United States, U.S. officials warn. A classified war simulation was held this month to assess the ramifications of an attack on Iran by Israel, The New York Times reported Tuesday. Officials in charge of the simulations said the so-called war game was designed to predict possible outcomes of an Israel-Iran conflict. A war was not the only possible outcome, officials stressed, adding that the two-week war game was not designed as a rehearsal for American military action. Nonetheless, the results of the exercise has raised fear among some American officials, including Gen. James N. Mattis, who commands all American forces in the Middle East, Persian Gulf and Southwest Asia, the newspaper said. After the war game ended, officials said Mattis told colleagues an Israeli first strike would likely have dire consequences across the region and for U.S. forces there. Ultimately, the war game showed military officials the unpredictable and uncontrollable nature of a strike by Israel, and a counterstrike by Iran, the officials said. Iran is the focus of a great deal of attention from Israel, the United States and other nations because of its alleged efforts to secure nuclear military capability. Iran denies it has nuclear ambitions.