TAMPA – Former U.S. ambassador to the United Nations John Bolton said on Tuesday that U.N. Secretary-General Ban Ki-moon’s decision to visit Iran to attend an international conference is his “worst mistake” since being at the helm of the U.N.

This week, Tehran is hosting a four-day gathering of the Non-Aligned Movement (NAM), an alternative international organization consisting of 120 nations seeking to weaken Western influence. The Secretary-General is expected to attend at a time when Iran is marching toward nuclear weapons capability.

“It legitimizes Iran,” Bolton said when the Washington Examiner asked him about the planned visit. “Number one, for the Non-Aligned Movement to make Iran its president. It tells you a lot about the Non-Aligned Movement and about the U.N. and it legitimizes Iran when the Secretary General of the United Nations goes there. It was a mistake for him to do. I’ve known Ban Ki-moon for 20-plus years. This is the worst mistake he’s made since becoming Secretary-General.”

President Obama has tried to argue that his outreach to Iran in the early stages of his presidency gained the U.S. international credibility, which helped lead to tougher sanctions against the Islamist regime. But the Secretary-General’s visit undermines efforts to isolate Iran.

“The administration’s policy is based on such an illusion that I don’t anticipate any real change before the election or before the election of Gov. Romney,” Bolton said. “But the risk is that Iran is very very close to achieving its objective of deliverable nuclear weapons and this simply encourages them to believe they will not face meaningful international sanctions, that they’ll find ways to avoid the sanctions. And I’m afraid that’s right.”

The visit also comes as Israel is facing a decision on whether or not to launch a military strike against Iran to prevent it from obtaining nuclear weapons capability, which could pose an existential threat.

“Israel is going to make a decision based on physics,” Bolton argued. “That is, they’ll wait until the last possible minute, but they won’t wait past the last possible minute. But I don’t think they’re going to calculate it based on the American political calendar. I think they’ll calculate it based on where they think Iran is in getting a nuclear weapon.”

He added, “the situation is changing so rapidly, that I just hope Iran doesn’t reach weapons capability before January 20th,” a reference to Inauguration Day.