The threatening tweet, sent late Sunday and written in all capital letters, was quickly hailed Monday by Israeli Prime Minister Benjamin Netanyahu, who praised the US leader's "tough stand."

But some analysts warned that Trump's words could backfire if they are not followed up with action.

The saber-rattling began when Iranian President Hassan Rouhani cautioned Trump not to "play with the lion's tail," saying that conflict with Iran would be the "mother of all wars" -- prompting the furious salvo from the US leader.

"NEVER, EVER THREATEN THE UNITED STATES AGAIN OR YOU WILL SUFFER CONSEQUENCES THE LIKES OF WHICH FEW THROUGHOUT HISTORY HAVE EVER SUFFERED BEFORE," Trump warned Rouhani.

"WE ARE NO LONGER A COUNTRY THAT WILL STAND FOR YOUR DEMENTED WORDS OF VIOLENCE & DEATH. BE CAUTIOUS!"

Iranian General Gholam Hossein Gheypour, head of the country's powerful Basij militia, then accused Trump of carrying out "psychological warfare" with his tweets -- while saying Trump was "not in a position to act."

Trump's National Security Advisor John Bolton backed him up on Monday, insisting that the Republican president would make good on his threats, meaning Tehran "could pay the price" for any misstep.

So what do all the warnings and counter-threats mean?

For some analysts in Washington, Trump is simply trying to redirect the conversation after a week of dire headlines over his much-maligned summit with Russia's Vladimir Putin and a relative lack of progress on North Korea.

"Frustrated by no progress w/NK; angered by negative push back post Helsinki, Trump is looking to vent, act tough, and change channel," said Aaron David Miller, a former US diplomat and Middle East negotiator for several administrations.

"If nothing else, Trump's ALL CAPS tirade reflect(s) reality that US has no Iran policy. Empty/ridiculous US rhetoric in response to same from Iran."

- 'Stop threat inflation' -

In May, Trump -- who has made Iran his public enemy number one -- announced the US withdrawal from what he called a "defective" multinational nuclear deal with Tehran, and moved to reinstate punishing sanctions.

Under Trump, many suspect the US government is hoping for regime change in Iran.

On Sunday, Secretary of State Mike Pompeo said only: "Our hope is that ultimately the regime will make meaningful changes in its behavior both inside Iran and globally."

For Miller, the "one/two punch" from Trump and Pompeo showed a "lack of a coherent US policy" on Iran.

"US should have 3 redlines for possible military action against Iran; and ridiculous Iranian rhetoric isn't one of them," Miller wrote.

"Preventing terror against the US; interruption of oil supply; stopping Iran from getting nuclear weapon. Otherwise stop threat inflation/ridiculous rhetoric."

After speaking with European officials about Trump's warnings, International Crisis Group president Rob Malley said diplomats on the continent were not "really taking it seriously."

In Europe, Trump's tirade is seen as a way to distract from controversy over his summit with Putin and the ongoing Mueller investigation into possible collusion between the Trump campaign and a Russian effort to sway the 2016 election.

"One can only hope they're right," Malley said.

- Saber-rattling -

While US ties with Iran and North Korea are different on several fronts, the words used by Trump to denigrate Tehran are similar in tone to those he directed a little more than a year ago at North Korean leader Kim Jong Un.

Several observers noted the similarities between the threats on Iran, and Trump's "maximum pressure" campaign towards Pyongyang.

In September 2017, in his first speech to the United National General Assembly, Trump threatened to "totally destroy" North Korea.

Nearly a year on, Trump has met Kim -- who he once called "Rocket Man" on a "suicide mission" -- for a landmark summit in Singapore, and follow-up talks are underway between the two sides.

However, concrete progress has been scant so far on denuclearization of the Korean peninsula -- a goal Kim pledged to work towards.

On Monday, Trump took aim at The Washington Post for highlighting the lack of solid results and reporting, citing unnamed officials, that the US president was frustrated by it.

"The Fake News is saying, without ever asking me (always anonymous sources), that I am angry because it is not going fast enough. Wrong, very happy!" he tweeted.