A Senate briefing by the Trump administration Tuesday about the escalation in tensions with Iran appears certain to kick off another round of sparring over the president’s war powers.

When asked last week whether President Donald Trump could strike Iran using existing authorities from the authorization for use of military force that was enacted after 9/11, the chairman of the Senate Foreign Relations Committee reflected on the history of disputes between the executive and legislative branches.

“You could write books on that question, couldn’t you? I’ve sat through dozens and dozens and dozens of hours of testimony, argument, legal briefings on that issue,” Idaho Republican Jim Risch said in a brief interview. “This question of the authority of the president versus the authority of the Congress has been argued since George Washington’s time. It is not resolved.”

Risch said Trump would obviously have authority in the event the United States finds itself responding to an attack from Iran.

“You have constitutional arguments, and you have statutory arguments, and it would entirely depend upon the conditions on the ground,” he said.

“If American forces are attacked, the president doesn’t need any more authority than what he’s got to respond to that, and I know this president and I can tell you he will not hesitate to respond to that.”

From the archives: Doing nothing is doing something — Trump, Congress and the use of force

‘Came out of nowhere’

Ahead of the scheduled all-senators briefing Tuesday, lawmakers seemed to be receiving disparate levels of information. A member of the Intelligence Committee, Risch seemed to be familiar with the material that led to the partial evacuation of the U.S. embassy in Baghdad last week.

But Democrats, such as Foreign Relations member Christopher S. Murphy of Connecticut, say that while recent Iranian actions are unacceptable, they believe the intelligence does not show the kind of urgent threat that has been implied by the Trump administration, particularly national security adviser John Bolton.

“I’m listening to Republicans twist the Iran intel to make it sound like Iran is taking unprovoked, offensive measures against the U.S. and our allies. Like it just came out of nowhere,” Murphy said Monday on Twitter. “I’ve read the intel too. And let me be clear — that’s not what the intel says.”

Murphy expanded on that somewhat during an interview with CQ Roll Call.

“The president’s Iran policy is all about escalation without any strategy. He doesn’t know what his endgame is here, and there’s not a realistic outcome where there is a negotiation,” the senator said. “He’s backing the Iranians into a corner, and it’s not clear how he’s going to get them out.”

Murphy is one of several Democrats to have criticized in particular the administration’s decision to withdraw from the Iran nuclear agreement, negotiated during the Obama administration.

“I can’t understand why [Trump] deliberately made such a mess out of Iran policy and put us on the precipice of conflict,” the Connecticut Democrat said.“It’s a really dangerous moment.”

NDAA markup

The first tests for the Trump administration’s Iran policy and any potential military authorization on Capitol Hill this week will likely come behind closed doors, as the latest developments coincide with the closed markup of the fiscal 2020 defense authorization bill at the Senate Armed Services Committee.

One of the panel’s members is Sen. Tim Kaine, a Virginia Democrat with a longstanding interest in fighting against “zombie war” authorizations and who has pushed presidents of both parties on war powers questions. On Monday, Kaine called the idea of another U.S. war in the Middle East “lunacy.”

“You’ll see a discussion of Iran as part of the NDAA markup,” Kaine said last week. “There may be other things, too.”

While he did not get into the specifics of what he may propose adding to the defense policy bill, Kaine said the public would know soon enough.

“Amendments that are offered, they’re all made public as soon as it’s open, and how everybody votes on the amendments are made public,” he said.

Sen. Benjamin L. Cardin, a senior member of the Foreign Relations Committee, said in an interview Sunday that he still hoped Congress would reassert some of its authority in war powers debates.

“We’ve seen presidents take a 2001 authorization for use of military force, which was really aimed at Afghanistan and Taliban, and use that to go after ISIS in Syria or go after ISIS in Northern Africa, which was clearly not congressional intent,” the Maryland Democrat said on C-SPAN’s “Newsmakers” program. “But to use military force against Iran — there is no authorization for the use of military force.”

Cardin noted that while the president would have authority to respond to a sudden threat, the Trump administration appears to be planning for action. Kaine also said that, in his view, the intent of Congress with the earlier authorization was clear.

“There was no intent by anybody in the Congress in 2001 that that authorization to go after the people who perpetrated the 9/11 attack would apply to Iran, and the text of it clearly does not specifically suggest any of that,” Kaine told CQ Roll Call.

But without getting into details, Risch said there is more intelligence than what has been publicly reported regarding Iran’s activities.

“That is the tip of the iceberg. When these situations are assessed, it is not a single item that moves the needle. It is a conglomerate of things, and a wide spectrum of reporting,” the Idaho senator told reporters.

Katherine Tully-McManus contributed to this report.