A classified Senate briefing on Iranian plots against the United States turned into a tense clash between top U.S. officials and lawmakers frustrated with President Trump’s strategy toward Tehran.

“I would say there was a lot of heat in that room,” Sen. Ted Cruz, R-Texas, told the Washington Examiner following the Tuesday afternoon briefing.

Key congressional Democrats suggested that President Trump’s administration was preparing for military conflict with the regime based on faulty intelligence or even false pretenses after ambiguous U.S. warnings that Iranian proxies might attack American personnel in Iraq. Secretary of State Mike Pompeo and acting Defense Secretary Patrick Shanahan sought to allay that suspicion in separate meetings, first with House lawmakers and then the Senate Tuesday afternoon.

“Today I walked them through what the Department of Defense has been doing since May 3, when we received credible intelligence about threats to our interests in the Middle East and to American forces, and how we acted on that credible intelligence,” Shanahan told reporters after the Senate briefing. "That intelligence has borne out in attacks, and I would say it’s also deterred attacks. We have deterred attacks based on our re-posturing of assets, deterred attacks against American forces.”

The controversy shifted in the briefing to complaints that they didn’t communicate with Congress enough in recent weeks and a broader protest against the administration’s withdrawal from the 2015 Iran nuclear deal. Vermont Sen. Bernie Sanders, a top contender for the 2020 Democratic presidential nomination, was among the most aggressive in raising the specter of being misled into a conflict with Iran.

“Most Americans know way back when we were lied to about the situation in Vietnam and we went into a war which ended up costing us 59,000 lives, based on a lie,” he said. “In 2003, we were lied to in terms of Iraq supposedly having weapons of mass destruction.”

Sanders refused to answer whether he believes such lies are being told now. “I won't talk about what we heard in the meeting,” he said. “But let me just say that I worry very much that, intentionally or unintentionally, we create a situation in which a war will take place.”

Senate Minority Leader Chuck Schumer avoided that controversy entirely, focusing only on the frustration that the administration didn’t provide more information to lawmakers over the last three weeks.

“I told the people who were briefing us that I thought the consultation with the American people and the Congress was inadequate,” the New York Democrat told reporters in a brief appearance, without taking additional questions. “Both the American people and the Congress read about a lot of actions in the newspapers and had no idea what was going on. I told them they had to make it better next time.”

Shanahan acknowledged that desire for more information. “We heard feedback that they’d like more conversation,” he said. “They’d also like us to be more communicative with the American public, and we agreed to do more of that.”

Maryland Sen. Ben Cardin, a senior Democrat on the Foreign Relations Committee, conceded that the meeting was a “very helpful” survey of the intelligence reports and U.S. responses.

Another lawmaker confirmed that the meeting was testy, but in this telling the confrontation was bipartisan and focused more on the administration’s policies than suspicions that they are fabricating intelligence.

“A number of them questioned the conclusions of the administration about the reaction of the Iranians and what it might lead to,” a Democratic senator, speaking on condition of anonymity, said after the briefing. “I think there's a lot of us with real misgivings about how serious this is and how much is a creation of the administration's own provocative policy.”

Shanahan stressed that the administration, which has deployed an aircraft carrier strike group to the Persian Gulf and threatened devastating consequences for attacks on Americans, is trying to avoid a conflict.

“Our biggest focus at this point is to prevent Iranian miscalculation,” he told reporters. “We do not want the situation to escalate."

Cruz kept the focus on Democratic hostility to Trump and their fidelity to the nuclear agreement that former President Barack Obama’s team negotiated with Iran.

“Far too many congressional Democrats are invested in appeasement for Iran, which manifests in effectively defending the mullahs against maximum pressure,” he told the Washington Examiner.