By Louis Charbonneau

UNITED NATIONS (Reuters) - The U.N. on Friday urged all sides in the dispute over Iran's nuclear program to tone down "shrill war talk," reacting to this week's clashes at the world body between Israeli Prime Minister Benjamin Netanyahu and Iran's President Mahmoud Ahmadinejad.

"It's obvious that harsh tones and rhetoric are not going to be helpful, that is quite clear," said U.N. spokesman Martin Nesirky when asked about Netanyahu's speech on Thursday to the General Assembly.

"What is also clear is that Iran needs to prove to the international community that its nuclear program is for peaceful purposes," Nesirky said.

Using a cartoonish diagram of a bomb, Netanyahu suggested in his speech that Israel might take military action to prevent Iran from reaching the point where it has enough enriched uranium for a bomb. He indicated that point could come by the spring or summer of 2013.

"Even without a chart, the secretary-general in his quite forceful remarks to the General Assembly on Tuesday made very clear that there does indeed need to be a toning down of the rhetoric from all sides," Nesirky said.

"He referred to the shrill war talk of recent weeks," Nesirky said, referring to U.N. chief Ban Ki-moon.

Ban met with Iranian President Mahmoud Ahmadinejad on Sunday and warned him of the dangers of incendiary rhetoric. Ahmadinejad disregarded Ban's caution, predicting on Monday that Israel would be "eliminated."

U.S. President Barack Obama followed on Tuesday with a warning to Tehran that it would do what it has to do to prevent Iran from getting an atomic weapon.

Iran's U.N. mission responded to Netanyahu's speech, saying Tehran was strong enough to defend itself and that it reserved the right to retaliate with full force against any attack.

Iran rejects allegations by Western nations and Israel that it is seeking the capability to produce an atomic weapon. Tehran insists its nuclear ambitions are limited to the peaceful production of medical isotopes and electricity.

(This version of the story removes the paragraph that mistakenly attributed market comments to Nesirky.)

(Additional reporting by Michelle Nichols; Editing by David Brunnstrom and Christopher Wilson)