Ahmadinejad said "the Iranian nation is a powerful nation and has quite an effect in the world conversation.
"We are prepared to use all our might and power to resolve world tensions and establish long lasting peace and security in the world".
The US and its allies suspects Iran intends to make a nuclear bomb.
Tehran denies the charge, but Iran's refusal to halt its nuclear programme has sparked talk of possible US or Israeli strikes on its nuclear sites.
Ahmadinejad dismissed such suggestions, saying: "Who dares to attack Iran? Who even dares to think about it?"
Successive Israeli governments have argued that Iran must be denied the means to make atomic weapons in order to preserve Israel.
But an opinion poll in Israel on Sunday found that only one in five Israeli Jews believes a nuclear-armed Iran would try to destroy their country.
The poll showed only 21 per cent of Israelis believe Iran "would attack Israel with nuclear weapons with the objective of destroying it", the Institute for National Security Studies, which commissioned the poll, said.
Asked how a nuclear-armed Iran would affect their lives, 80 per cent of people said they expected no change, while 11 per cent said they would consider emigrating and nine per cent said they would consider relocating inside Israel.
Ahmadinejad was declared winner of Iran's presidential vote on Friday and has said the vote was free and fair.
But his re-election has sparked protests across the country by supporters of Mir Hossein Mousavi, his main challenger.
The unexpected result and its violent aftermath have raised questions about how Iran will respond to the diplomatic overtures of Barack Obama, the US president, who had urged Iran's leadership "to unclench its fist".