Iran's Supreme Leader says if attacked by the United States, Iran will respond by striking U.S. interests all over the world.

Speaking to Iranian air force commanders Thursday, Ayatollah Ali Khamenei said "the enemy knows well that the Iranian nation will give a comprehensive response to any aggression."

The United States has been increasing pressure on Iran, accusing it of meddling in Iraq and of seeking to develop nuclear weapons. However, U.S. Defense Secretary Robert Gates said last week the United States has no plan for war with Iran.

Also Thursday, Iranian media are reporting that Tehran has become aware of an Israeli-U.S. spy ring operating on Iranian border areas.

The media are quoting Iran's intelligence minister Gholam Hossein Mohseni Ejehe who says Iran has arrested a number of Iranians who were trying to leave the country for espionage training.

The Iranian supreme leader spoke on the second and final day of war games carried out by Iran's Revolutionary Guards in the Persian Gulf and Sea of Oman.

The guards say they have successfully tested a new Russian-built air defense system and also missiles that one commander said are capable of sinking "big ships."

Some information for this report was provided by AFP, AP and Reuters.