"If anyone allows himself to commit even a tiny offense against Iran's legitimate interests, borders and sacred land, our armed forces will break his hand before he pulls the trigger," Ahmadinejad said during the parade.
The phrase "legitimate interests" is Iranian parlance for the country's nuclear program, which the West says is a cover for developing nuclear weapons. Iran, which denies the charge, already is under three sets of sanctions by the U.N. Security Council over the issue.
Washington and its Western allies are pushing for quick passage of a fourth set of sanctions to underline the international community's resolve.
But Ahmadinejad said Sunday that sanctions only help Iran achieve self-sufficiency.
"Those who once imposed sanctions, today should open their eyes and see our nation's technical achievements," he said.
Both the United States and its ally Israel say they support a diplomatic solution to the nuclear standoff with Iran but cannot rule out the military option.
"Today, Iran is not in a position to show softness toward its enemies," said Ahmadinejad, but added that threats made against Iran's nuclear facilities amounted to only "psychological warfare."
Sunday's parade commemorated the start in 1980 of Iran's ruinous eight-year war with neighboring Iraq.
Meanwhile, the official IRNA news agency reported that on the sideline of the parade, the air force chief of the Iran's elite Revolutionary Guards, Gen. Hossein Salami, rejected the notion that Iran had any ambitions for nuclear weapons, describing them as "ineffective."
"Any report about Iran's intention to use nuclear weapon is a sheer lie," he said, while adding that "our missiles are able to target the enemy's points in the region."