President Trump’s decision to strike Iran without congressional authorization and little consultation has divided Congress and deepened rifts inside both parties, touching off a searing debate over the role of the military and how much power the legislative branch should wield over the use of American forces.

Some leading Democrats have reacted with outrage at Mr. Trump’s unilateral authorization, calling it an unconstitutional overstepping of his authority and demanding a briefing and a swift vote on whether to approve any further military action in Iran. Top Republicans, who have rushed to cede congressional power to the president at the start of his term, have instead called the strikes on Iran justified and appropriate, arguing that Congress should have no say in the matter.

“The commander in chief has Article II responsibilities,” Speaker Mike Johnson told reporters on Monday, referring to the section of the Constitution covering presidential power.

Voicing strong opposition to voting on a bipartisan measure to reassert Congress’s war powers, he continued: “They’re very serious and important, especially in times like this. I think he used that authority judiciously.”

He dismissed the resolution, sponsored by Representatives Thomas Massie, Republican of Kentucky, and Ro Khanna, Democrat of California, as “all politics,” signaling that he was not inclined to allow their bid to force a vote on the military strikes. And he noted that presidents of both parties had undertaken significant military actions without congressional approval, often with little pushback from their allies on Capitol Hill.

Mr. Johnson’s comments came just after Representative Hakeem Jeffries, the minority leader, signaled support for such a vote and castigated Mr. Trump for his lack of consultation with Congress. He also claimed that the administration still had not given top leaders the customary classified briefing that accompanies such military operations.