The comments by Iranian supreme leader Ayatollah Ali Khamenei came the same day that another top official, Iran's ambassador to the United Nations, Javad Zarif, warned in a column in The New York Times that efforts to isolate Iran would backfire on the United States, increasing sectarian tensions in the volatile Middle East, including Iraq.
The United States and Iran have been in an increasingly tense standoff over Iran's nuclear program. The tensions have worsened recently because of U.S. allegations of Iranian influence in Iraq.
The United States has denied it has any plans to strike Iran militarily but has sent an additional aircraft carrier to the Persian Gulf in what U.S. officials call an effort to show strength in the face of rising Iranian regional influence.
Speaking to a gathering of Iranian air force commanders, Khamenei said: "The enemy knows well that any invasion would be followed by a comprehensive reaction to the invaders and their interests all over the world."
But one Iran expert believes Khamenei's remarks may be motivated primarily by domestic politics.
Bernie Kaussler, an associate fellow at the University of St. Andrews' Institute for Iranian Studies, tells CBSNews.com that Iran's supreme leader may be more interested in satisfying his core supporters than going to war with America.
Khamenei has been frequently at odds with President Mahmoud Ahmadinejad — whose fiery anti-U.S. rhetoric and aggressive politics with the West has represented a sharp divergence from Iranian policy of recent years.
Khamenei's own stance may more accurately reflect the will of the majority of Iranians; a desire to maintain the "political status quo, and not export the Islamic revolution," according to Kaussler.
But both men have to keep a very influential, and large, conservative religious constituency happy, and taking a tough stance on the U.S. is an effective means of achieving this goal.
In another sign of the tensions with the U.S., Iran's intelligence minister said Thursday the government had detected a network of U.S. and Israeli spies and had detained a second group of people who planned to go abroad for espionage training, state television reported. It gave few details.
The allegation comes just a few days after an Iranian diplomat was detained in Baghdad in an incident that Iran blamed on U.S. forces. The Americans have denied involvement in the diplomat's detention.