UN Secretary-General Ban Ki-moon Iran's leaders' comments as "offensive and inflammatory.""(Ban) believes that all leaders in the region should use their voices at this time to lower, rather than to escalate, tensions," it said in a statement.
"In accordance with the United Nations Charter, all members must refrain from the threat or use of force against the territorial integrity or political independence of any state."
Ahmadinejad delivered his speech at a Tehran rally held in honor of Al-Quds (Jerusalem) Day, marked each year on the last Friday of Ramadan in accordance with a tradition established by Ayatollah Ruhollah Khomeini, the late supreme leader of Iran.
Ahmadinejad referred to Israel as a western "tool to dominate the Middle East" and an "insult to all humanity."
"Today, Israel and the Zionist entity are against the preservation of all human rights and human dignity," IRNA quoted Ahmadinejad as saying at the event.
During the same speech, AFP quoted him as saying: "The Zionist regime and the Zionists are a cancerous tumor. Even if one cell of them is left in one inch of (Palestinian) land, in the future this story (of Israel's existence) will repeat."