By Joshua Berlinger, CNN

(CNN) -- Iran has shot back at US President Donald Trump, dismissing his all-caps Twitter warning that the country would suffer consequences if it continued to threaten the US, saying it was unimpressed by the late-night tweet.

"COLOR US UNIMPRESSED," Iran's Foreign Minister Mohammad Javad Zarif tweeted Monday night, employing Trump's penchant to use all capital letters in his tweets.

"The world heard even harsher bluster a few months ago. And Iranians have heard them -- albeit more civilized ones -- for 40 yrs. We've been around for millennia & seen fall of empires, incl our own, which lasted more than the life of some countries. BE CAUTIOUS."

Zarif's online comments are the latest in the escalating war of words between Washington and Tehran. Zarif's tweet comes less than a day after Trump posted a furious Twitter warning to Iranian President Hassan Rouhani.

"NEVER, EVER THREATEN THE UNITED STATES AGAIN OR YOU WILL SUFFER CONSEQUENCES THE LIKES OF WHICH FEW THROUGHOUT HISTORY HAVE EVER SUFFERED BEFORE," Trump tweeted after returning to the White House from a weekend at his golf resort in Bedminster, New Jersey.

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

White House press secretary Sarah Sanders said Monday Trump was responding to forceful comments Rouhani made earlier Sunday, in which he warned Trump "do not play with the lion's tail, because you will regret it eternally."

Later Monday morning, national security adviser John Bolton said Trump told him that "if Iran does anything at all to the negative, they will pay a price like few countries have ever paid before."

Foreign policy challenge

Iran experts are unsure if the 280 character-limit broadsides are more likely to foreshadow conflict or if they are a way to project strength before engaging Tehran diplomatically.

Trump employed similarly heated rhetoric when responding to threats and missile tests by North Korea last year.

"The reality is he's such an erratic President that you could see him dropping bombs on Iran or you could see him trying to build hotels in Iran," said Karim Sadjadpour, an Iran expert at the Carnegie Endowment.

"He's much more impulsive than he is strategic."

When asked if Trump risked inciting war with Iran, White House press secretary Sarah Sanders told reporters Monday morning, "if anybody is inciting anything, look no further than to Iran."

She wouldn't directly say whether Trump consulted with his national security team before the tweet. He speaks with them daily, she said, but declined to give any details about any steps Trump is looking to take with Iran.

"The President's been, I think, pretty strong since day one in his language toward Iran. He was responding to comments made from them, and he's going to continue to focus on the safety and security of American people," Sanders said at the White House briefing later Monday. She declined repeated questions about whether Trump would consider meeting with Rouhani.

Trump came into office vowing to take a hard line on Iran and scrap the Obama-negotiated nuclear deal of 2015, a promise he fulfilled in May.

The agreement forced Iran to curtail its uranium enrichment capacity to prevent it developing nuclear weapons, and imposed stringent verification processes, in exchange for relief on crippling sanctions.

One of Trump's many criticisms of the accord, known as the Joint Comprehensive Plan of Action, was that it did not do enough to stop Iran from funding extremist groups throughout the Middle East.

The other signatories to the deal, including France, the UK and Germany, have vowed to stand by it.

'Something that resembles the mafia'

On Sunday night, US Secretary of State Mike Pompeo launched a blistering attack on Iran's religious rulers. The speech, which came hours after Rouhani's threat but before Trump's tweet, has been interpreted as part of a concerted effort within the Trump administration to step up economic and political pressure on Iran.

"The level of corruption and wealth among regime leaders shows that Iran is run by something that resembles the mafia more than a government," Pompeo said during an appearance at the Ronald Reagan Presidential Library and Museum.

Like Trump, Pompeo is a longstanding critic of the nuclear deal.

"We are asking every nation who is sick and tired of the Islamic Republic's destructive behavior to join our pressure campaign. This especially goes for our allies in the Middle East and Europe, people who have themselves been terrorized by violent regime activity for decades," said Pompeo.

Pompeo, the former director of the CIA, also used the speech to allege that the county's leaders have made billions of dollars from corrupt dealings.

The secretary accused Supreme Leader Ayatollah Ali Khamenei, Iran's head of state, of maintaining a personal off-the-books hedge fund worth $95 billion.

"These hypocritical holy men have devised all kinds of crooked schemes to become some of the wealthiest men on Earth while their people suffer."