UN chief Ban Ki-moon on Thursday urged Iran to comply with UN resolutions demanding it curb its nuclear activities, warning that heightened international rhetoric over the issue risked degenerating into "war."
He said Tehran should build confidence in its nuclear programme by "fully complying with the relevant (UN) Security Council resolutions and thoroughly cooperating with the IAEA."
Otherwise, he warned, "a war of words can quickly spiral into a war of violence."
Ban also reprimanded Iran for "outrageous" comments denying the Holocaust and Israel's right to exist, and called on the two arch-nemeses to drop threats against each other.
"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 in a speech before a Non-Aligned summit in Tehran.
"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," he added.
Ban spoke as Iran's supreme leader Ayatollah Ali Khamenei on Thursday slammed the "overt dictatorship" of the UN Security Council in a speech opening th Tehran summit that included Ban himself in the audience.
"The UN Security Council has an irrational, unjust and utterly undemocratic structure, and this is an overt dictatorship," Khamenei told the 120-member NAM summit.
Iran is in a showdown with the Security Council over its disputed nuclear programme, which has resulted in four sets of Security Council resolutions imposing sanctions on it for pursuing uranium enrichment.
Khamenei charged that "the control room of the world (the Security Council) is under the control of the dictatorship of some Western countries" -- implying permanent council members the United States, France and Britain.
State television showed Ban looking nonplussed as Khamenei delivered his speech.
The NAM, which represents much of the developing world, has long championed a reform of the United Nations to take power away from the UN Security Council and bolster the say of the UN General Assembly, where its members are better represented.
Khamenei's criticism of the UN's top table followed a meeting he had with Ban on Wednesday in which the UN leader bluntly told Iran to take "concrete" steps to ease the showdown over the nuclear issue.