Lawmakers are divided over the U.S. airstrike in Baghdad that killed Iranian military leader Qassem Soleimani, the head of Iran's elite Quds military force and one of the most powerful figures in the Islamic Republic. The strike, which drew a warning of "crushing revenge" from Iran and condemnation from Iraq's government, has raised concerns about potential retaliatory attacks from Iran and encroachment by the president on Congress' power to declare war.

President Trump did not brief all congressional leaders before the airstrike and had not made any direct remarks, except on Twitter by Friday morning. The major military action came as a surprise to many lawmakers on Capitol Hill. The top Democrat on the Senate Intelligence Committee, Mark Warner, of Virginia, learned of the strike from the Associated Press wires, according to an aide.

Warner told CBS News that he was "deeply disappointed" that the administration didn't notify the Gang of Eight bipartisan group of Senate leaders beforehand. The Gang of Eight, which includes Warner, is briefed on classified matters by the White House and executive branch.

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A senior administration official directly involved in congressional outreach regarding the strike told CBS News the Gang of Eight briefing — which includes Democratic and Republican leaders and the top Democrats and Republicans on the intelligence committees — will only happen when all the members are assembled in person next week.

Warner doesn't dispute that Soleimani was a foe of the U.S. "I believe there was a threat," he said, but he still has questions about the circumstances of the strike.

"The question of the time and place of us taking action on that threat is something that is still subject to some debate," Warner said.

House Speaker Nancy Pelosi spoke with Defense Secretary Mark Esper on Thursday evening. She warned in a statement that the airstrike might lead to "further dangerous escalation of violence," adding that this action was taken without the full consultation of Congress.

"The full Congress must 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," Pelosi said.

Last year, when the U.S. initiated an operation to take out the top ISIS leader Aku Bakr al-Baghdadi, the president also chose not to inform congressional Democrats beforehand. When the Obama administration took out Osama bin Laden in 2011, then-Congressman Mike Rogers, the chairman of the Senate Intelligence Committee, said the entire "Gang of Eight" had been briefed on the plans, although they were not all briefed at the same time, according to the Congressional Research Service.

Some Democrats, like Senator Tom Udall, pressed for Congress to "reclaim its Constitutional war powers. Senator Tim Kaine, who's concerned that President Trump could be "stumbling into a war with Iran," introduced a war powers resolution to force a debate and a vote before taking further military action in Iran.

"We're now at a boiling point, and Congress must step in before Trump puts even more of our troops in harm's way. We owe it to our servicemembers to have a debate and vote about whether or not it's in our national interest to engage in another unnecessary war in the Middle East," Kaine said in a statement.

Republicans supported the president's action, saying that Mr. Trump had approved a proportionate response to aggression from Iran. Senator Jim Risch, the chairman of the Senate Foreign Relations Committee, praised Mr. Trump for his "decisive action and the successful outcome." Senator Lindsey Graham, a staunch ally of the president, also tweeted praise of the strike and was among the few lawmakers briefed on the operation.

"I appreciate President @realDonaldTrump's bold action against Iranian aggression. To the Iranian government: if you want more, you will get more," Graham tweeted. Graham told "Fox & Friends" Friday that he was told of the operation when he visited Mar-a-Lago earlier this week.

House Minority Leader Kevin McCarthy, who posted pictures to Instagram of himself with the president at Mar-a-Lago Thursday evening, said in a statement that the airstrike is "not only a statement to those seeking to attack America, but it also marks the stark difference between this administration and previous ones."

In the past, Mr. Trump has been willing to pursue high-value terrorist targets, but he has also avoided moves likely to expand U.S. military actions, as shown by his attempts to withdraw forces from Afghanistan and his decision to pull special forces out of northern Syria a few months ago.

The move to assassinate Soleimani marks a change for the president, and it comes as he campaigns for re-election this year. It draws the U.S. and Iran closer to war and increases the risks for Americans in the Middle East and elsewhere.

The Pentagon said Mr. Trump ordered the strike as a "decisive defensive action to protect U.S. personnel," accusing Soleimani of "actively developing plans to attack American diplomats and service members in Iraq and throughout the region." The White House said that the president had the authority to strike under "applicable statutes," specifically, the Authorization for the Use of Military Force Against Iraq Resolution of 2002.

Tucker Reals, Major Garrett and Alan He contributed to this report