Sen. Elizabeth Warren (D-MA) raises her hand as former Vice President Joe Biden speaks during the Democratic Presidential Debate at Tyler Perry Studios November 20, 2019 in Atlanta, Georgia.

Soleimani led an elite branch of Iran's armed forces, the Quds Force, and has been blamed for the deaths of many, including Americans, across the Middle East.

Top 2020 Democratic White House contenders slammed President Donald Trump 's decision to take out Iran's top commander, Gen. Qasem Soleimani, in an airstrike in Baghdad , saying the attack will likely lead to escalation.

Former Vice President Joe Biden, who leads the Democratic field in national polling averages, said Soleimani "deserved to be brought to justice for his crimes against American troops and thousands of innocents throughout the region," but the decision to kill him "is a hugely escalatory move in an already dangerous region."

Biden tweet

"President Trump just tossed a stick of dynamite into a tinderbox, and he owes the American people an explanation of the strategy and plan to keep safe our troops and embassy personnel, our people and our interests, both here at home and abroad, and our partners throughout the region and beyond," Biden added.

Sen. Elizabeth Warren echoed Biden's concerns. She called Soleimani "a murderer," but added that "this reckless move escalates the situation with Iran and increases the likelihood of more deaths and new Middle East conflict."

Warren tweet

Sen. Bernie Sanders said a conflict in the Middle East "could cost countless lives and trillions more dollars."

Sen. Amy Klobuchar slammed the timing of the attack and said the United States should focus on protecting "U.S. military and diplomatic personnel in Iraq and throughout the region."

Klobuchar tweet

Entrepreneur Andrew Yang said Friday the United States has "been in a constant state of armed conflict for 19 years at a disastrous cost to both our people and our resources. This must end."

Yang tweet

Former South Bend, Indiana, Mayor Pete Buttigieg said in a statement on Friday that "this must not be the start of another endless war. We must act wisely and deliberately, not capriciously or through Twitter."

Pete tweet

Former New York City Mayor Mike Bloomberg said that he hopes "the president has carefully thought through the national security implications of this attack for our country," but given Trump's track record, "there is every reason to deeply concerned."

Bloomberg tweet

Rep. Tulsi Gabbard, who has been critical of American military involvement in the Middle East, said on Fox News on Friday: "I don't believe the American people want to go to war with Iran."

The White House and the Trump campaign didn't immediately respond to requests for comment on the Democratic candidates' statements.

But Trump tweeted that "Soleimani has killed or badly wounded thousands of Americans over an extended period of time, and was plotting to kill many more...but got caught!"

Trump tweet

In a statement Thursday, House Speaker Nancy Pelosi called for Congress to "be immediately briefed on this serious situation and on the next steps under consideration by the administration, including the significant escalation of the deployment of additional troops to the region."

The Pentagon confirmed the U.S. killing of Soleimani on Thursday night. Hours after the Pentagon's announcement, Iran's Foreign Minister Mohammad Javad Zarif said on Twitter that the attack was "extremely dangerous & a foolish escalation."

"The US bears responsibility for all consequences of its rogue adventurism," he said.

Zarif tweet

— CNBC's Amanda Macias and Kevin Breuninger contributed to this report.