The supreme leader of Iran warned on Friday that war would have devastating consequences, adding to rising tension as American officials expressed alarm at Israeli saber-rattling.

The Washington Post's David Ignatius wrote in a column that U.S. Defense Secretary Leon Panetta believed Israel would strike Iran before its nuclear program becomes impervious to attack. CNN confirmed Ignatius' account, citing a senior administration official.

Iran's Supreme Leader Ayatollah Ali Khamenei struck a bellicose tone during a Friday sermon, denouncing threats from the United States and saying war itself will be 10 times as detrimental to the U.S.

The Zionist regime is really the cancerous tumor of this region and it needs to be removed and will be removed, Khamenei said.

Israeli Defense Minister Ehud Barak renewed his warning in a Thursday speech that Iran was swiftly approaching what is referred to as the immunity zone, in which Iran's nuclear program becomes sophisticated enough that a military attack would not be enough to halt it.

Whoever says 'later' may find that later is too late, Barak said.

The Obama administration prefers to wait for tough new sanctions to take effect and force Iran into a diplomatic compromise. The administration has not rejected the possibility of a military strike, and Khameini was referencing Obama's frequent assertion that a military option is on the table when he mentioned American threats.