National Security Adviser John Bolton delivered a no-holds-barred warning to Iran at a major summit in New York on Tuesday, telling the regime in a fiery speech that "we are watching, and we will come after you" and that there will be "hell to pay" if it continues on its current course.

Bolton's saber-rattling remarks came hours after President Trump, in his own dramatic address to the U.N. General Assembly, called on "all nations to isolate Iran's regime as long as its aggression continues."

Tensions have dramatically escalated in recent weeks between Iran and the U.S., as well as its regional allies. Iranian Supreme Leader Ayatollah Ali Khamenei has claimed that an attack Saturday at an Iranian military parade, which left dozens of Iranian military personnel dead, was carried out by militants trained by Israel and the Gulf states, and supported by the U.S.

"If you cross us, our allies, or our partners ... yes, there will indeed be hell to pay." — National Security Adviser John Bolton

American officials have denied having played any role.

On Tuesday, a threatening video showing a simulated Iranian ballistic missile strike on Israel and Saudi Arabia was posted to the Twitter account of the semiofficial state Fars News Agency, before it was quickly deleted.

And a top military official in Iran warned the U.S. and Israel on Monday that there would be a “devastating” response to the parade attack.



WATCH: TRUMP CALLS ON UN TO 'ISOLATE' IRANIAN REGIME

In his speech to the United Against Nuclear Iran (UANI) annual summit, Bolton took aim at the threatening rhetoric long used by Khomeini and other top Iranian politicians.

"According to the mullahs in Tehran, we are 'the Great Satan,' lord of the underworld, master of the raging inferno," Bolton said. "So, I might imagine they would take me seriously when I assure them today: If you cross us, our allies, or our partners; if you harm our citizens; if you continue to lie, cheat and deceive, yes, there will indeed be hell to pay." Applause broke out in the room.

He continued: "The ayatollahs have a choice to make. We have laid out a path toward a bright and prosperous future for all of Iran, one that is worthy of the Iranian people, who have long suffered under the regime’s tyrannical rule."

Iran, Bolton said, "brazenly supports the criminal Assad regime in Syria" and was "complicit in Assad's chemical weapons attacks on his own people." He also called Iran the world's "worst kidnapper of U.S. citizens."

JOHN KERRY SLAMMED FOR CONDUCTING 'SHADOW DIPLOMACY' WITH IRAN -- IS IT ILLEGAL?

Bolton also dismissed the now-defunct Obama-era nuclear deal with Iran in no uncertain terms as "the worst diplomatic debacle in American history."



Last month, the Trump administration restored major sanctions against Iran that had been suspended under former President Barack Obama's 2015 nuclear deal, threatening to further unravel the Islamic country's already-struggling economy. Bolton on Tuesday said the sanctions had already had a "crippling" effect on Iran's economy, and threatened to send its housing market into a recession.

Thousands protested across Iran in the wake of the decision, as soaring unemployment and poverty prompted demonstrators to torch police vehicles and burn tires. At least one person was shot and killed in the protests, with some shouting, "Mullahs get lost!" and "Death to the dictator!" the Fars news agency reported at the time.

WATCH: VIDEO ON SEMI-OFFICIAL STATE NEWS AGENCY SHOWS SIMIULATED IRAN MISSILE ATTACK

Iranian lawmakers, on video, burned American flags and chanted, "Death to America" after Trump ended the deal.

Even more severe U.S. sanctions against Iran's banking and energy sectors are slated to go into effect in the first week of November, including restrictions on Iran's oil industry that could cut off a crucial source of hard currency. The sanctions already reimposed target Iranian trade in automobiles, gold and other key metals.

"We expect purchasers of Iranian oil to reduce to their imports to zero by November 4, or face the risk of sanctions," Bolton said. "After November 5, President Trump intends to pursue addiitonal sanctions" beyond those that existed prior to the Iranian nuclear deal, Bolton added, as he vowed a "maximum pressure" campaign against those who defy the sanctions.

The nuclear deal, which Trump has derided since his presidential campaign as a "horrible, one-sided arrangement," was touted by the Obama administration as a breakthrough in preventing Iran from obtaining a nuclear bomb.

But it contained numerous provisions -- including "weasel words," Bolton said Tuesday -- that White House officials found insufficient, such as limited inspection mechanisms to ensure Iran's compliance with the deal, as well as sunset provisions that would lift various restrictions on Iran's nuclear program in as little as 10 years.

TRUMP BRUSHES OFF LAUGHTER FROM UN AUDIENCE AS HE TOUTS ACHIEVEMENTS

Trump charged Tuesday that Iran used funds from the nuclear deal to repress its people and "fund havoc and slaughter in Yemen and Syria," and said Iran has increased its military budget by more than 40 percent since the deal was reached.

"We cannot allow the world's leading sponsor of terrorism to possess the planet's most dangerous weapons," Trump said. "Just can't do it."

The Iran nuclear deal, Bolton said Tuesday, "did nothing to address the regime’s destabilizing activities or its ballistic missile development and proliferation. Worst of all, the deal failed in its fundamental objective: permanently denying Iran all paths to a nuclear bomb.

"The United States is not naïve," Bolton added. "We will not be duped, cheated, or intimidated again. The days of impunity for Tehran and its enablers are over. The murderous regime and its supporters will face significant consequences if they do not change their behavior. Let my message today be clear: We are watching, and we will come after you."

Secretary of State Mike Pompeo also spoke at the UANI summit earlier on Tuesday, and criticized other nations for "enabling" Iranian-sponsored terrorism by working with Iran to bypass U.S. sanctions.

"Just a few months ago, authorities across Europe arrested several Iranian operatives ... as part of a plot to plant a bomb at a political rally in France," Pompeo said, before praising France for taking retaliatory economic action against Iran.

"Unfortunately, just last night, I was disturbed and indeed deeply disappointed to hear remaining parties in the [nuclear] deal announce they are setting up a special payment system to bypass U.S. sanctions," Pompeo said. "This is one of the most counterproductive measures imaginable for regional and global peace and security."

Fox News' Greg Norman contributed to this report.