By Hossein Jaseb
Ahmadinejad also said at a military parade the region could handle its own security without U.S. and other foreign forces although he did not name arch foe, the United States.
Iran is embroiled in a row over its nuclear programme, which the United States says is a covert bid to make nuclear weapons. Iran, the world's fourth biggest oil producer, denies this and says its aim is to generate electricity.
Washington says it wants diplomacy to end the dispute but has not ruled out military action. Analysts say the possibility of strikes seem remote after a U.S. intelligence report last year said Iran halted a nuclear weapons programme in 2003.
"We saw that oppressive, arrogant … and satanic powers planned, using a suspicious excuse to gain dominance over the world's energy reserves …, brought their troops to our region," Ahmadinejad said at the annual ceremony.
"Today they have failed," he said in the televised address shortly before warplanes and helicopters flew overhead and troops marched passed the podium set up south of Tehran.
Equipment on show included several missiles on trucks but did not include the Shahab-3, which officials have said is Iran's longest range projectile capable of hitting targets 2,000 km (1,250 miles) away.
"The Iranian nation has reached a level that none of the world powers dare to threaten (it)," he said, adding that Iran would respond "powerfully" to any attack.
He said Iran would stand by its neighbours "to spread peace and security in the region without the presence of foreigners".
Iran has regularly demanded the United States and its Western allies withdraw from Iraq and the region, as well as calling for a security pact with nearby Gulf Arab states.
Gulf Arab states, which are mostly Sunni Muslim, have yet to take up the offer and have long been wary of Shi'ite Muslim Iran's intentions in the area.
The president said Iran was capable of domestically making most of its main military equipment needs and said this included tanks, aircraft and other weaponry, some of which was included in the parade.
(Additional reporting by Zahra Hosseinian, Writing by Edmund Blair)
