Washington (CNN) The US airstrike that killed Iran Quds Force commander Qasem Soleimani generated starkly different reactions along party lines Thursday night, with Republicans heaping praise on President Donald Trump and Democrats expressing concerns about the legality and consequences of the attack.

The Pentagon confirmed in a statement that Trump had ordered the strike, saying Soleimani "was actively developing plans to attack American diplomats and service members in Iraq and throughout the region. General Soleimani and his Quds Force were responsible for the deaths of hundreds of American and coalition service members and the wounding of thousands more."

"I appreciate President @realDonaldTrump's bold action against Iranian aggression," GOP Sen. Lindsey Graham of South Carolina, a fierce Trump ally, wrote in a tweet Thursday. "To the Iranian government: if you want more, you will get more."

Two sources tell CNN that key Senate staff on relevant committees on national security and appropriations, along with leadership staff, will be briefed Friday afternoon in a classified setting by administration officials.

Some key members of Congress -- such as Senate Minority Leader Chuck Schumer, a New York Democrat who is a member of the congressional Gang of Eight leaders, who are briefed on classified matters -- had not been made aware of the attack ahead of time. It's not clear how many other lawmakers had advance notice of the strike.

House Speaker Nancy Pelosi called for an immediate briefing to the full Congress on the US strike. In a written statement Thursday, Pelosi said that the airstrike "risks provoking further dangerous escalation of violence" and took issue with the strike being carried out without consultation with Congress.

The Pentagon added that "this strike was aimed at deterring future Iranian attack plans" and the US "will continue to take all necessary action to protect our people and our interests wherever they are around the world."

GOP praises Trump's action

Republicans reacted with almost uniform praise for Trump.

Sen. Ben Sasse, Republican of Nebraska, said in a news release that "General Soleimani is dead because he was an evil bastard who murdered Americans" and "the President made the brave and right call, and Americans should be proud of our servicemembers who got the job done."

Sasse added, "Tehran is on edge - the mullahs have already slaughtered at least a thousand innocent Iranians - and before they lash out further they should know that the U.S. military can bring any and all of these IRGC butchers to their knees."

His comments were echoed by Sen. Tom Cotton, Republican of Arkansas, who said in a statement that Soleimani "masterminded Iran's reign of terror for decades, including the deaths of hundreds of Americans."

"Tonight, he got what he richly deserved, and all those American soldiers who died by his hand also got what they deserved: justice," Cotton said. "America is safer now after Soleimani's demise."

Senate Foreign Relations Committee chair, Republican Sen. Jim Risch of Idaho, said Soleimani's death "presents an opportunity for Iraq to determine its own future free from Iranian control."

Sen. Mitt Romney of Utah, who sits on the Senate Foreign Relations Committee, called Soleimani a "depraved terrorist" who was "doubtlessly planning operations to further harm our citizens and allies."

The Republican senator added that it's "imperative" that the US and its allies "articulate & pursue a coherent strategy for protecting our security interests in the region," adding that he will be pressing the Trump administration for additional details.

Democrats weigh in on Soleimani killing

Democrats pushed back on Republican sentiments about the attack, stressing the potential consequences and lambasting the decision to carry out the strike without congressional authorization.

Sen. Chris Murphy of Connecticut emphasized that Soleimani "was an enemy of the United States" in a tweet before stating, "The question is this - as reports suggest, did America just assassinate, without any congressional authorization, the second most powerful person in Iran, knowingly setting off a potential massive regional war?"

In a more explicit statement, Sen. Tom Udall of New Mexico said, "President Trump is bringing our nation to the brink of an illegal war with Iran without any congressional approval as required under the Constitution of the United States."

He added: "Such a reckless escalation of hostilities is likely a violation of Congress' war making authority -- as well as our basing agreement with Iraq -- putting U.S. forces and citizens in danger and very possibly sinking us into another disastrous war in the Middle East that the American people are not asking for and do not support."

On the campaign trail, Democratic former Vice President Joe Biden said "no American will mourn" Soleimani but that the strike that killed him is a "hugely escalatory move."

"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 said in a statement.

"I'm not privy to the intelligence and much remains unknown, but Iran will surely respond. We could be on the brink of a major conflict across the Middle East. I hope the Administration has thought through the second- and third-order consequences of the path they have chosen."

Other presidential candidates expressed similar misgivings, including Sens. Elizabeth Warren of Massachusetts , Bernie Sanders of Vermont, and Cory Booker of New Jersey.

"Trump promised to end endless wars, but this action puts us on the path to another one," Sanders said in a statement in which he used the word "assassination" to refer to the death of Soleimani.

Booker, speaking on "CNN Tonight," said Soleimani had "American blood on his hands," but he questioned Trump's ability to handle the fallout of the attack.

"We also know there are larger challenges, strategic challenges in that region, and we have a President who has failed to show any larger strategic plan, and under his leadership, with his so-called maximum forces, Iran has become a more dangerous, more influential regime in that region," Booker told CNN's Victor Blackwell.

Sen. Marco Rubio, a Florida Republican, took aim at the Democratic responses, positing that "some are so blinded by hatred of Trump that they argue he has done something sinister."

"It's crazy," Rubio said. Total derangement."