Former US secretary of state Henry Kissinger called on Thursday for "serious" international negotiations with Iran to prevent it from becoming nuclear in "the foreseeable future," warning of a dangerous situation which could force an Israeli military strike."Unilateral intervention by Israel would be a desperate last resort, but the Iranians have to understand that if they keep using the negotiations to gain time to complete a nuclear program then the situation will become extremely dangerous," Kissinger, 89, told the World Economic Forum in Davos. "If Iran acts as a nation and not as a revolutionary cause, there is no reason for America or other permanent members of the UNSC to be in conflict with it, nor any countries in the region. On that basis I would hope that a negotiated solution would be found in a measurable time."He added: "For 15 years, the permanent members of the United Nations Security Council (UNSC) have declared that a nuclear Iran is unacceptable, but it has been approaching," he said. "In a few years, people will have to come to a determination of how to react, or the consequences of non-reaction. I believe this point will be reached in a very foreseeable future."