If the US walks away from the nuclear deal with Iran, there is a real risk of war, UN Secretary General António Guterres said in an exclusive interview with the BBC on Thursday morning.Calling the Iran agreement an "important diplomatic victory" Guterres argued that, unless there is a good alternative, the deal should be maintained."If one day there is a better agreement to replace it, it's fine. But we should not scrap [the deal] unless we have a good alternative," the UN Secretary General stated, emphasizing that "We face dangerous times."White House officials said on Wednesday that US President Donald Trump had all but decided to withdraw from the 2015 Iran nuclear accord by May 12, as reported by Reuters.The only reason the president would choose to keep the United States in the pact would be "alliance maintenance" with France, the report stated.However, if US sanctions relief were to be lifted and thus the nuclear deal abandoned, this would trigger a backlash by Iran which could resume its nuclear arms program or "punish" US allies in Syria, Iraq, Yemen and Lebanon, diplomats said.Technically, Trump must decide by May 12 whether to renew "waivers" suspending some of the US sanctions on Iran. One of the White House officials who spoke on condition of anonymity said it was possible Trump will end up with a decision that "is not a full pullout" but was unable to describe what that might look like.A presentation by Prime Minister Benjamin Netanyahu on Monday about documenting evidence of Tehran's past nuclear arms program could give Trump a fresh argument to withdraw, even though UN inspectors say Iran has complied with the terms of the deal. Iran has denied ever seeking nuclear weapons and accuses its arch-foe Israel of stirring up world suspicions against it.The pact between Iran and six major powers - Britain, China, France, Germany, Russia and the United States - was among former US president Barack Obama's signature foreign policies but has been described by Trump as "one of the worst deals I have ever witnessed."The White House official said Trump was "most of the way there toward pulling out of the deal but he hasn't made the decision" and that he "seems poised to do it, but until a decision is made by this president it is not final."Top aides are not aggressively seeking to talk Trump out of withdrawal because he seems intent on it, a second White House official said.Reuters contributed to this report.