The Wall Street Journal reports U.S. military leaders are increasingly concerned that Israel is preparing to attack Iran over apparent U.S. objections. According to the Journal, President Obama, Defense Secretary Leon Panetta and other top officials have delivered a string of private messages to Israeli leaders warning about the dire consequences of a strike. Joint Chiefs of Staff Chairman Martin Dempsey is set to visit Israel this week. The United States has also stepped up contingency planning to safeguard U.S. facilities in the region in case of an Israeli attack. Meanwhile, the United States and Israel have postponed what had been described as the largest joint military exercise ever carried out by the two nations.