"I think we've got to be prepared to take aggressive military action against the Iranians to stop them from killing Americans in Iraq," Lieberman told Bob Schieffer. "And to me, that would include a strike into... over the border into Iran, where we have good evidence that they have a base at which they are training these people coming back into Iraq to kill our soldiers."
The Indepedent former Democrat from Connecticut said that he was not calling for an invasion of Iran, but he did say the U.S. should target specific training camps.
"I think you could probably do a lot of it from the air, but they can't believe that they have immunity for training and equipping people to come in and kill Americans," Lieberman said.
Lieberman, who has been one of Congress's most outspoken supporters of the Bush administration's Iraq war policies, said that continuing the fight in Iraq and confronting Iran are necessary for achieving a wider peace in the Middle East.
If the U.S. does not act against Iran, "they'll take that as a sign of weakness on our part and we will pay for it in Iraq and throughout the region and ultimately right here at home," Lieberman said.
He said that he has seen evidence that the Iranians are supplying insurgents and foreign fighters in Iraq.
"By some estimates, they have killed as many as 200 American soldiers," he said.
The Senator said he was not calling for an end to the limited diplomatic efforts that are underway between Washington and Tehran.
"We can tell them we want them to stop that, but if there's any hope of the Iranians living according to the international rule of law and stopping, for instance, their nuclear weapons development, we can't just talk to them," Lieberman said. "If they don't play by the rules, we've got to use our force, and to me that would include taking military action to stop them from doing what they're doing."