Clark, the former Supreme Allied NATO Commander and chair of the Board of Advisers of VoteVets.org, Monday said in a statement that Lieberman, the former Democratic candidate for vice president in the 2000 presidential election, had been irresponsible in saying Sunday that such action against Iran might be necessary.

"Sen. Lieberman's saber rattling does nothing to help dissuade Iran from aiding Shiite militias in Iraq, or trying to obtain nuclear capabilities. In fact, it's highly irresponsible and counter-productive, and I would urge him to stop," Clark said.

"This kind of rhetoric is irresponsible and only plays into the hands of (Iranian) President (Mahmoud) Ahmadinejad and those who seek an excuse for military action," the retired four-star general said.

"What we need now is full-fledged engagement with Iran," he said. "All options are on the table, but we should be striving to bridge the gulf of almost 30 years of hostility before, and only when all else fails should there be any consideration of other options."

"Only someone who never wore the uniform or thought seriously about national security would make threats at this point," Clark said. "What our soldiers need is responsible strategy, not a further escalation of tensions in the region. Sen. Lieberman has to act much more responsibly and tone down his threat machine."

In his comments, Lieberman said, "If (the Iranians) 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."