Iran says it will respond firmly to the United States if it becomes directly involved in Israel's military campaign, the Iranian ambassador to the United Nations in Geneva said on Wednesday. +Get the most important news from Switzerland in your inbox "For the moment, we are not thinking of any scenario other than defending ourselves," Iran's ambassador to the UN in Geneva, Ali Bahreini, said. "The United States is complicit," he told reporters in the Swiss city. "Without them, Israel can do nothing." Iran is "closely monitoring" the US involvement in this affair and how this might change. The army will assess when it considers that Washington, which supports Israel militarily, can be considered a "direct" party to the conflict, Bahreini added. He said he was "confident that it will respond, firmly and appropriately". Israel launched its air war, its largest ever on Iran, on Friday after saying it had concluded the Islamic Republic was on the verge of developing a nuclear weapon.