* Ban plans to attend non-aligned summit in Iran-envoys
* U.S., Israel want Ban to boycott Tehran summit
* U.N. chief has criticized Iran for anti-Israel remarks
By Louis Charbonneau
UNITED NATIONS, Aug 22 (Reuters) - U.N. Secretary-General Ban Ki-moon plans to attend a summit meeting of leaders of non-aligned developing nations in Tehran next week, defying calls from the United States and Israel to boycott the event, U.N. diplomats said on Wednesday.
A spokesman for Iran's U.N. mission said it appeared that Ban would be attending the summit next week, though he declined to speak on behalf of the secretary-general's office.
Several other U.N. diplomatic sources said that barring any unexpected scheduling changes, Ban would attend the meeting of some 120 non-aligned nations in Tehran.
"It's a very important bloc of nations," a diplomatic source told Reuters on condition of anonymity. "Of course the SG (secretary-general) is going. He can't not go."
A Security Council diplomat said it was important for the secretary-general to go. He said Ban should not turn his back on the entire non-aligned movement because one member, Iran, happens to have a president who doubts the Holocaust and questions Israel's right to exist.
Ban's spokesman declined to comment.
Diplomats said they did not expect Ban to raise Iran's nuclear program, which Iran says is peaceful and Western powers and their allies fear is aimed at nuclear weapons, and its leaders' anti-Israeli remarks during his public speech during the non-aligned summit.
Such rebukes would be better left to Ban's expected private bilateral meeting with Iranian President Mahmoud Ahmadinejad in Tehran, envoys said.
The Tehran summit, which Egyptian President Mohamed Mursi will also attend, takes place Sunday through Friday. Mursi is the first Egyptian head of state to visit Tehran since the 1979 Islamic revolution.
BAN UNDER PRESSURE TO BOYCOTT SUMMIT
Earlier this month, Israeli Prime Minister Benjamin Netanyahu urged Ban to cancel his plans to participate in the Tehran non-aligned summit, according to Israeli media reports.
U.S. State Department spokeswoman Victoria Nuland made clear to reporters in Washington last week that the United States would also like the U.N. chief to boycott the event.
"The fact that the meeting is happening in a country that's in violation of so many of its international obligations and posing a threat to neighbors ... sends a very strange signal with regard to support for the international order, rule of law, et cetera," Nuland said.
"We've made that point to participating countries," she said. "We've also made that point to Secretary-General Ban Ki-moon."
Nuland added that if Ban does go, "we hope he will make the strongest points of concern."
Last week Ban sharply criticized Iranian Supreme Leader Ayatollah Ali Khamenei and President Mahmoud Ahmadinejad, describing their latest verbal attacks on Israel as "offensive and inflammatory."
Ahmadinejad said there was no place for the Jewish state in a future Middle East, echoing previous remarks he has made about Israel. He has also repeatedly called into question the Nazi extermination of Jews during World War Two - the Holocaust.
Khamenei said last week that Israel would one day be returned to the Palestinian nation and would cease to exist.
Separately, Alireza Miryousefi, spokesman for Iran's U.N. mission in New York, defended the Tehran summit in a letter to the editor of The Washington Post. He was responding to an editorial in the newspaper, which said Ban's presence in Tehran "will dignify a bacchanal of nonsense."
Miryousefi said the Post's editorial board "unjustifiably smeared Iran and mocked the upcoming Non-Aligned Movement summit in Tehran.
"By bringing dozens of world leaders together, the summit promises to make significant contributions to the movement's lofty objectives," he wrote.