United Nations Secretary General Ban Ki-moon delivered a sharp rebuttal to Iranian Supreme Leader Ayatollah Ali Khamenei on Thursday, after Khamenei delivered a speech denouncing Israel, the UN and the US at the Non-Aligned Movement summit in Tehran.

“I strongly reject any threat by any [UN] member state to destroy another, or outrageous comments to deny historical facts such as the Holocaust,” Ban said.

“Claiming another UN member state does not have the right to exist or describe it in racist terms is not only utterly wrong but undermines the very principles we have all promised to uphold,” the UN chief added.

Khamenei, who has final say on all state matters in Iran, accused Israel of being made up of “bloodthirsty wolves,” a day after Ban asked the cleric to tone down his rhetoric against Israel.

With Ban in attendance, Khamenei blasted the UN Security Council, calling it an illogical, unjust and defunct relic of the past used by the United States and Zionists “to impose its bullying manner on the world.”

Khamenei accused the United States of talking about human rights “when what they mean is Western interests. They talk of democracy when what they have is military intervention in other countries.”

He also reiterated that Iran has never sought nuclear weapons but will continue to develop its peaceful nuclear energy program, saying that the country considers the use of nuclear weapons to be “a big and unforgivable sin.”

Khameini added that Iran’s “motto is nuclear energy for all and nuclear weapons for none.”

Iran says the gathering in Tehran shows that Western sanctions have not resulted in Iran’s diplomatic isolation.

The West suspects Iran is developing a nuclear weapons program, a charge Tehran denies. On Wednesday Ban urged Iran to take concrete steps to prove to the world that the Iranian program is for civilian use.