"Last week, the Trump administration conducted a provocative and disproportionate military airstrike targeting high-level Iranian military officials," Pelosi said in a statement Wednesday.
"The administration took this action without consulting Congress," she added. "This action endangered our service members, diplomats and others by risking a serious escalation of tensions with Iran. Since then, the president has made clear that he does not have a coherent strategy to keep the American people safe, achieve deescalation with Iran and ensure stability in the region."
Members of Congress were briefed Wednesday by top Trump administration officials, including Defense Secretary Mark Esper, Secretary of State Mike Pompeo, CIA Director Gina Haspel and Army Gen. Mark Milley, chairman of the Joint Chiefs of Staff, on the justification for the airstrike that killed Soleimani, the leader of Iran's elite and secretive Quds Force.
In an address to the nation Wednesday morning, Trump vowed to keep up the pressure on Tehran with "punishing" new sanctions on top of heavy economic restraints already in place, but he didn't suggest any additional military action in response to Iran's overnight missile attack.
"Iran appears to be standing down, which is a good thing for all parties concerned and a very good thing for the world," Trump said. "No American or Iraqi lives were lost because of the precautions taken, the dispersal of forces and an early warning system that worked very well."
In her statement, Pelosi said members of Congress "have serious, urgent concerns about the administration's decision to engage in hostilities against Iran and about its lack of strategy moving forward. Our concerns were not addressed by the president's insufficient War Powers Act notification and by the administration's briefing today."
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Pelosi said the resolution would be marked up by the Rules Committee on Wednesday night and go to the floor for a vote Thursday.
Many Democrats complained after the drone strike on Soleimani that the White House hadn't notified Congress beforehand. Pelosi said Saturday that "raises more questions than it answers" and "prompts serious and urgent questions about the timing, manner and justification of the administration's decision to engage in hostilities against Iran."
Pelosi also criticized the administration's decision to classify the notification, saying the move "compounds our many concerns, and suggests that the Congress and the American people are being left in the dark about our national security."
Democrats and some Republican lawmakers said Wednesday that they also found the administration's briefing lacking.
"I had hoped and expected to receive more information outlining the legal, factual and moral justification for the attack and left somewhat unsatisfied on that front," Sen. Mike Lee, R-Utah, said, adding that "it was probably the worst briefing I've seen, at least on a military issue, in the nine years I've served in the United States Senate."
Lee said he would vote for a war powers resolution sponsored Sen. Tim Kaine, D-Va., which is similar to the House measure. "That briefing changed my mind," he said.
Sen. Rand Paul, R-Ky., who was standing alongside Lee, agreed, saying, "Today, this is Senator Lee and I saying we are not abdicating our duty."
The House resolution aims to limit the president's military action against Iran without Congress' approval unless there is an imminent threat against the United States or U.S. forces. It adds Trump is required by law "to consult with Congress 'in every possible instance' before introducing United States armed forces into hostilities," aside from countering immediate threats.
According to House Democrats, the administration said it was authorized to kill Soleimani because of the 2002 Authorization of Use of Military Force Against Iraq because the attack occurred in that country — an argument Democrats said is particularly egregious.
Pelosi indicated that she could bring up two other bills to limit the president's war powers. One, by Rep. Barbara Lee, D-Calif., would repeal the 2002 Iraq War authorization and another, by Rep. Ro Khanna, D-Calif., would block funding for an unauthorized U.S. war with Iran.
Iran's retaliatory missile attack thrust the path forward on the war powers resolution into "uncertainty," Rep. Eliot Engel, D-N.Y., chairman of the Foreign Affairs Committee, said earlier Wednesday, with some Democratic members raising concerns about restricting the president right after the United States was attacked.
The war powers resolution appears to have satisfied the concerns of some moderate Democrats who had expressed reservations about moving too fast.
"I'm not prepared to endorse a particular resolution right now," Rep. Tom Malinowski, a moderate freshman from New Jersey, said Wednesday morning. "A number of us have been talking about the best way to frame this. It has to take into account what happened last night. It has to take into account where we are right now."
Rep. Hakeem Jeffries, D-N.Y., said: "We won't move forward until we have the robust support of every corner of the caucus. We want to act in a responsible fashion on behalf of the safety and security of the American people. That is what this is all about."
In his remarks Wednesday, Trump continued to make his case against Iran and defended the killing of Soleimani, calling him the "world's top terrorist." He warned that the United States was developing "many hypersonic missiles" to counter Iran should it seek to obtain a nuclear weapon and continue its state-sponsored terrorism.
"The civilized world must send a clear and unified message to the Iranian regime: Your campaign of terror, murder, mayhem will not be tolerated any longer," Trump said. "It will not be allowed to go forward."