Iranian Supreme Leader Ayatollah Ali Khamenei rejected U.S. demands that Tehran abandon uranium enrichment, saying doing so would destroy “a great achievement” and vowing that Iranians will refuse and “slap” anyone who proposes it. “Negotiations with the US regarding the nuclear issue, and perhaps other matters, are a dead end,” Khamenei added in a speech addressing the nation Tuesday. Why It MattersThe Iranian leader’s comments signal a non-negotiable stance on its nuclear program, escalating tensions with Western powers, looming over this month’s U.N. General Assembly in New York. “Countries seeking to build nuclear weapons increase enrichment to even 90%. The Iranian nation will slap anyone who suggests such a thing and refuse to accept it.”Trump: “My position is very simple.