TEHRAN -- Iran's defense minister warned the United States Tuesday to respect the "red line" of the Islamic Republic's border with Iraq, saying his country was prepared for "any eventuality".

In the event of a war with Iraq, Rear Admiral Ali Shamkhani also warned Washington against "using armed Iranian opposition groups based in Iraq" to attack Iran.

"When it comes to security matters, the Americans have to understand that there is a "red line" between Iran and Iraq," Ali Shamkhani was quoted as saying by the official news agency IRNA.

Asserting that a U.S. presence in Iraq would "increase the threat to and vulnerability of Iran in terms of its security", he said Iran's military was "ready for any eventuality".

"We are capable of taking direct action as well as preventative action against American threats," and underlined that Iran had been dealing with U.S. threats since the 1979 Islamic Revolution. He said any U.S. attack on Iran "would lead to an unpredictable result for the United States and the security of the region."

But he insisted that Iran's vocal opposition to Washington's moves toward war with Iraq did not represent a major confrontation.

"You have to understand that to condemn an eventual U.S. military action does not signify a confrontation with the U.S. We have made every political effort to reduce the risk of war and avert an American strike," he said.

"In the current state of affairs, the level of hostilities between Iran and the United States is not so great for that country to begin military action some 10,000 kilometers (6,500 miles) from its borders," Shamkhani said.