TEHRAN — Iran’s president acknowledged on Tuesday that new sanctions imposed by Western powers were the most onerous ever but said they would have no impact on the Iranian position in a protracted dispute over its nuclear energy activities.

The statement by the president, Mahmoud Ahmadinejad, was his first public appraisal of the new European and American sanctions, which are aimed at crippling Iran’s oil industry. He spoke as Iran’s Islamic Revolutionary Guards Corps sought to punctuate defiance of Western pressure by test-firing missiles capable of hitting Israeli and American military bases in the Middle East. Clips of the missile launchings were broadcast on state television.

“The sanctions imposed on our country are the most severe and strictest sanctions ever imposed on a country,” Mr. Ahmadinejad said during a meeting with Intelligence Ministry officials in Tehran, reported by Iranian news services. “But the enemies’ assumption that they can put Iran in a weak position through these sanctions is false and is the result of their materialistic calculations.”

Mr. Ahmadinejad also said Iran should turn the sanctions into an “opportunity to eliminate the country’s current reliance on oil revenue and take away from the enemy the use of oil as a weapon for imposing sanctions.”