"I think it's incredibly dangerous," Representative Seth Moulton warned.
"That's a very serious issue if they continue to do that," Trump's national security adviser warned.
National security adviser John Bolton, Japanese Prime Minister Abe Shinzo and now the State Department have all contradicted the president.
The president's national security adviser also suggested Iran is still seeking a nuclear arsenal despite its adherence to the 2015 nuclear deal.
"If he's working towards a deal, as you say, it's a deal we don't know about," John Brennan said. "He basically said he wants denuclearization. That is not going to happen."
Buttigieg argued that "it wouldn't be the first time" that Trump has "lost control of an international dynamic."
The North Korean official referred to Bolton as more of a "security-destroying adviser" than a security adviser.
Harsh words follow Bolton's criticism of Pyongyang missile tests.
Last week, North Korea's official Korean Central News Agency published commentary blasting Biden as a "snob lacking even the most basic qualities of a human being, much less a politician."
"Iran is no threat to anybody in Iraq or elsewhere, and Iran is not preparing for any attacks anywhere," the spokesperson for Iran's mission to the United Nations said.
President Donald Trump is angry that military planning has seemed to outpace his diplomatic efforts, according to a new report.
The plans are separated into two categories and involve airstrikes, targeted incursions and setting U.S. forces up for a ground invasion.
"We are actually considering escalating with Iran in a war that would further destabilize the region and unleash God knows what in terms of chaos in a very troubled region already," Elise Jordan said.
War could become a fait accompli if Trump keeps Bolton in the White House.
Majid Takht Ravanchi, Iran's ambassador to the United Nations, warned the U.S. against repeating the mistakes of the Iraq War.
The president is reportedly frustrated with national security adviser John Bolton's overconfidence about toppling Venezuela's President Nicolás Maduro.
A spokesperson for Iran's national security body said John Bolton's announcement was "mostly meant to draw attention to himself."
"War with Iran is playing with fire, and it will burn all, and not just Iran," said Iranian lawmaker Alaeddin Boroujerdi.
"We are fully prepared to respond to any attack, whether by proxy, the Islamic Revolutionary Guard Corps, or regular Iranian forces," national security adviser John Bolton said.
"Tell the Bolivarian government and Nicolas Maduro what is necessary to be changed," the Venezuelan leader said.
National Security Adviser John Bolton accused a CNN host of picking a fight after he was pressed about a scheduled call with the Russians he mentioned just moments before on Fox News.
"They have all shown an interest in dragging the United States into a conflict," Javad Zarif told Fox News Sunday. "I do not believe that President Trump wants to do that. I believe that President Trump ran on a campaign promise of not bringing the United States into another war."
The group of 12 politicians asked Donald Trump to use Washington's influence within the Organization of American States to prevent Bolivian President Evo Morales from running for another term.
"This is a catastrophic departure from the very basis of international law," former Swedish Prime Minister Carl Bildt said in response to President Donald Trump's call to recognize Israel's sovereignty over the Golan Heights.
Bolton suggested that the Trump administration was ready to embrace a modern version of the Monroe Doctrine.
National Security Adviser John Bolton insisted President Donald Trump's Hanoi visit was somehow a "success" despite acknowledging that no denuclearization agreement was made and North Korea remains a threat to global stability.
Last month, President Donald Trump's national security adviser was spotted with a notepad that said, "5,000 troops to Colombia."
The U.S. listed the MEK, an Iranian opposition group pushing for regime change, as a terrorist organization until 2012.