The United States will not take Iran at its word over pledges of openness on a believed nuclear weapons programme, Secretary of State John Kerry said Thursday after Israel threatened to go it alone against Tehran. \"I assure (Prime Minister Benjamin) Netanyahu and the people of Israel that nothing that we do is going to be based on trust,\" the top US diplomat told reporters in Tokyo. \"This is going to be based on a series of steps to guarantee to all of us that we have certainty on what\'s happening.\"