During a speech delivered in the Western Iranian province of Javanroud, Ahmadinejad said: " The Islamic Republic of Iran is now a nuclear power, thanks to the hard work of the Iranian people and authorities."
The announcement of Iran as a "nuclear power" is bound to significantly escalate tensions between the West and Iran, and marks a dramatic stage in the Islamic Republic's nuclear campaign.
In recent days, the US military has begun to build up forces around the Gulf, in what is being seen as as a warning to Iran.
Ahmadinejad was also reported to have announced that "Iranian young scientists reached the zenith of science and technology and gained access to the nuclear fuel cycle without the help of big powers."
The Iranian president began the speech by saying that "the powerful Iranian nation resists bullying powers and will defend its rights, including the right to pursue peaceful nuclear technology," the IRNA said.
In a clear rejection of all diplomatic attempts to prevent Iran from going nuclear, Ahmadinejad added in his speech that "the Iranian nation will continue in its nuclear path powerfully and will celebrate a nuclear victory soon."
The IRNA said Ahmadinejad was in Javanroud for a three-day tour along with members of his cabinet.