2020 Democratic presidential candidates spoke out after President Trump Donald John TrumpBarr criticizes DOJ in speech declaring all agency power 'is invested in the attorney general' Military leaders asked about using heat ray on protesters outside White House: report Powell warns failure to reach COVID-19 deal could 'scar and damage' economy MORE on Thursday approved an airstrike in Baghdad that killed Gen. Qassem Soleimani, the head of Iran’s elite Quds Force.

The move is a major escalation of tensions between the U.S. and Iran, with Iran vowing "harsh retaliation" in response.

Former Vice President and Democratic front-runner Joe Biden Joe BidenThe Memo: Warning signs flash for Trump on debates Senate Republicans signal openness to working with Biden National postal mail handlers union endorses Biden MORE tweeted a statement late Thursday that “No American will mourn Qassem Soleimani's passing,” but cautioned that Trump’s order could leave the U.S. “on the brink of a major conflict across the Middle East.”

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“No American will mourn Qassem Soleimani’s passing. He deserved to be brought to justice for his crimes against American troops and thousands of innocents across the region. He supported terror and sowed chaos. None of that negates the fact that this is a hugely escalatory move in an already dangerous region,” Biden said.

My statement on the killing of Qassem Soleimani. pic.twitter.com/4Q9tlLAYFB — Joe Biden (@JoeBiden) January 2, 2020

The Pentagon confirmed late Thursday that Trump ordered the attack at Baghdad International Airport that killed Soleimani in addition to Abu Mahdi al-Muhandis, the deputy head of the Iran-backed Iraqi Popular Mobilization Forces.

Sen. Bernie Sanders Bernie SandersSenate Republicans signal openness to working with Biden Hillicon Valley: DOJ indicts Chinese, Malaysian hackers accused of targeting over 100 organizations | GOP senators raise concerns over Oracle-TikTok deal | QAnon awareness jumps in new poll Schumer, Sanders call for Senate panel to address election security MORE (I-Vt.) tweeted Thursday, warning that “Trump's dangerous escalation brings us closer to another disastrous war in the Middle East that could cost countless lives and trillions more dollars.”

“Trump promised to end endless wars, but this action puts us on the path to another one,” Sanders continued.

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Trump's dangerous escalation brings us closer to another disastrous war in the Middle East that could cost countless lives and trillions more dollars.



Trump promised to end endless wars, but this action puts us on the path to another one. — Bernie Sanders (@BernieSanders) January 2, 2020

Sen. Elizabeth Warren Elizabeth WarrenNo new taxes for the ultra rich — fix bad tax policy instead Democrats back away from quick reversal of Trump tax cuts It's time for newspapers to stop endorsing presidential candidates MORE (D-Mass.) joined Biden in condemning Soleimani, saying he was “a murderer, responsible for the deaths of thousands, including hundreds of Americans.”

“But this reckless move escalates the situation with Iran and increases the likelihood of more deaths and new Middle East conflict. Our priority must be to avoid another costly war,” she continued.



Soleimani was a murderer, responsible for the deaths of thousands, including hundreds of Americans. But this reckless move escalates the situation with Iran and increases the likelihood of more deaths and new Middle East conflict. Our priority must be to avoid another costly war. — Elizabeth Warren (@ewarren) January 2, 2020





"As a former military intelligence officer on the ground in Afghanistan, I was trained to ask the hard questions before acting. A Commander-in-Chief must do the same," Buttigieg said.

"Before engaging in military action that could destabilize an entire region, we must take a strategic, deliberate approach that includes consultation with Congress, our allies, and stakeholders in the Middle East," he added.

Statement from @PeteButtigieg on killing of Qassim Soleimani: pic.twitter.com/9k2tSEiPu6 — Chris Meagher (@chrismeagher) January 3, 2020

Entrepreneur Andrew Yang Andrew YangDoctor who allegedly assaulted Evelyn Yang arrested on federal charges The Hill's Campaign Report: Biden weighs in on police shootings | Who's moderating the debates | Trump trails in post-convention polls Buttigieg launches his own podcast MORE tweeted calling for resolving tensions in the region

War with Iran is the last thing we need and is not the will of the American people. We should be acting to deescalate tensions and protect our people in the region. — Andrew Yang (@AndrewYang) January 2, 2020

Sen. Cory Booker Cory Anthony BookerDemocratic lawmakers call for an investigation into allegations of medical neglect at Georgia ICE facility Black Voters Matter Fund deploying voter outreach caravans in 12 states to drive turnout Philanthropist Susan Sandler investing 0M in social justice organizations MORE (D-N.J.) appeared on MSNBC Thursday night, saying that the Iranian general has “American blood on his hands,” but Booker called on leaders to “look at the larger strategic situation in that area.”

“We have a president who has had, really, a failure in his Iranian policy, who has had no larger strategic plan and has made that region less stable and less safe, not only for Americans, but for other countries.”

We have a president who has no strategic plan when it comes to Iran and has only made that region less stable and less safe. More thoughts: pic.twitter.com/Cn25X4kOhQ — Cory Booker (@CoryBooker) January 3, 2020

Sen. Amy Klobuchar Amy KlobucharEPA delivers win for ethanol industry angered by waivers to refiners It's time for newspapers to stop endorsing presidential candidates Biden marks anniversary of the Violence Against Women Act, knocks Trump and McConnell MORE (D-Minn.) tweeted a statement saying “the timing, manner, and potential consequences of the administration’s actions raise serious questions and concerns about an escalating conflict,” adding that “The [Trump] Administration needs to fully consult with Congress on its decision-making, response plans, and strategy for preventing a wider conflict.”

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Author Marianne Williamson Marianne WilliamsonMarianne Williamson discusses speaking at People's Party Convention Fewer people watched opening night of Democratic convention compared to 2016 Marianne Williamson: Democratic convention 'like binge watching a Marriott commercial' MORE tweeted, "Prayers for peace. Killing of Qasem Solemani by US military was one of the most reckless irresponsible actions ever directed by a US President. Congress deserves condemnation for allowing it (NDAA) and Americans need to understand this: War with Iran would be totally disastrous."

Prayers for peace. Killing of Qasem Solemani by US military was one of the most reckless irresponsible actions ever directed by a US President. Congress deserves condemnation for allowing it (NDAA) and Americans need to understand this: War with Iran would be totally disastrous. — Marianne Williamson (@marwilliamson) January 3, 2020

Updated at 12:42 p.m.