President Trump tweeted on Tuesday that any "attack by Iran on anything American will be met with great and overwhelming force."

Why it matters: It's a new red line for Trump in the latest round of heightened tensions with Iran. The president previously called off a military strike in response to the downing of a U.S. drone, claiming the death toll would be disproportionate. His tweet on Tuesday strikes a markedly new tone.

"Iran leadership doesn't understand the words "nice" or "compassion," they never have. Sadly, the thing they do understand is Strength and Power, and the USA is by far the most powerful Military Force in the world, with 1.5 Trillion Dollars invested over the last two years alone. The wonderful Iranian people are suffering, and for no reason at all. Their leadership spends all of its money on Terror, and little on anything else. The U.S. has not forgotten Iran’s use of IED's & EFP's (bombs), which killed 2000 Americans, and wounded many more. Iran's very ignorant and insulting statement, put out today, only shows that they do not understand reality. Any attack by Iran on anything American will be met with great and overwhelming force. In some areas, overwhelming will mean obliteration. No more John Kerry & Obama!"

Context: The U.S. imposed new sanctions against Iran's leadership and Ayatollah Ali Khamenei on Monday. Iran's foreign ministry responded by saying these sanctions have led to the "permanent closure of the path of diplomacy," while President Hassan Rouhani blasted the White House's move as "useless" and indicative of a "mental handicap."

Go deeper... Timeline: How Trump and Tehran came to the brink of war