The US has condemned Ahmadinejad`s tirade against Israel, calling it "reprehensible", while UN chief expressed dismay.
"Iran and Syria`s blatant disregard for basic human rights is the real insult to humanity," he said.
In a late night statement, UN Secretary General, Ban Ki-moon said he is "dismayed" by the remarks threatening Israel`s existence.
"The Secretary-General condemns these offensive and inflammatory statements," said a statement issued by his spokesman.
"The Secretary-General believes that all leaders in the region should use their voices at this time to lower, rather than to escalate, tensions. 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," the UN statement said.
Meanwhile, top American Senator, Bobb Casey, in a letter to the UN Secretary General, urged him not to attend the upcoming Summit of the Non-Aligned Movement (NAM) in Tehran later this month.
"Iran has not complied with its obligations to the International Atomic Energy Agency, is an active state sponsor of terrorism, and continues to support the murderous regime of Bashar al-Assad," wrote Casey, Chairman of the US Senate Foreign Relations Subcommittee on Near Eastern, South and Central Asian Affairs.
"I am concerned that your presence in Tehran could serve to legitimise the actions of this regime at a critical time in the region and urge you to reconsider attending this conference," he wrote.