Senators from both sides of the aisle skewered senior State Department official Andrea Thompson at a hearing Wednesday on the Trump’s arms control policies, criticizing her for not fully answering their questions on the Trump administration’s arms control policies.

Thompson, who is undersecretary for Arms Control and International Security, had several testy exchanges with Democrats, notably with committee Ranking Member Sen. Bob Menendez (D-NJ). The senator exploded after she deferred one of his questions to Russia. “I’m not asking Russia about our national defense, I’m asking you!” he yelled, pointing his finger at her.

Testiness from Democrats was somewhat expected, due to partisan politics. But it was the sharp exchanges with some Republicans that surprised observers of the hearing, particularly with Sen. Ted Cruz (R-TX).

Cruz hammered Thompson on why the bureau she leads at the State Department has continued to advocate for waivers that allow Iran to continue nuclear research as part of the Iran nuclear deal that President Trump opposes and has pulled out of.

“Top State Department officials in your Bureau have stated that it is your policy to facilitate ‘international cooperation with Iran on a number of projects contemplated under the [Iran nuclear deal] that provide Iran opportunities to benefit from nuclear technology,” he said. “Elsewhere officials, including those in your Bureau, have touted the benefits of the so-called transparency as promised in the deal.”

“These positions appear to be in significant tension, if not direct conflict, with the positions of President Trump,” he added. “I find it troubling that we are continuing to implement parts of the nuclear deal, and I want to understand the basis for these decisions.”

Cruz noted that the waivers are hinged on Iran being considered a “member in good standing” to the Nuclear Non-Proliferation Treaty, and asked her whether she thought Iran was a member in good standing, noting the position of other Trump officials that it was not.

Thompson said there were “concerns,” before eventually agreeing that Iran was not in good standing. However, she said the waivers were in the “best interests” of the U.S. When pressed for an explanation, she repeatedly refused to discuss it in an open-setting, saying she would prefer to discuss it with him in a closed-door setting.

Cruz countered, saying, “With all respect, the American people care deeply about this. So I am perfectly happy to have classified briefings, but whether we are allowing Iran to do nuclear weapons in a bunker designed to create weapons of mass destruction to murder Americans is an issue of concern to 28 million Texans.”

“The American people are entitled to get an answer if it is the State Department’s position that that’s a good idea, the American people are entitled to know that,” he added.

After Thompson tried to assure Cruz that she would not do anything to harm U.S. interests, Cruz blasted it as “a stunning Orwellian position.”

“I don’t believe that’s true in any administration that every decision an elected official makes or an appointed official makes is by definition in the interest of the American people. And that’s one of the reasons Congress has oversight responsibility,” he said.

At the end of their exchange, Thompson appeared to flatly disagree with Cruz over whether it was in the U.S.’s best interests to have Iran continuing nuclear research at its Fordow nuclear bunker facility. Cruz asked:

Why would the State Department continue to give waivers to allow them to conduct nuclear research, particularly in the Fordow site? That I find staggering. It’s a bunker built in the side of a mountain. It’s not a medical research facility. It’s not a diaper factory. It is a bunker built to make nuclear weapons. And the State Department assigned waivers saying Iran, that the Ayatollah can continue to do nuclear research there. How is that possibly in the interest of the United States?

Thompson responded, “I would say that’s your assessment, Senator. I would not characterize it as such.”

“Well, that’s the problem,” he fired back.

The @StateDept is allowing #Iran to continue doing research in their nuclear bunker at Fordow, which Iran dug into the side of a mountain to build nuclear weapons. They are unwilling to explain to the American people why they’re doing it. pic.twitter.com/j8L2YvPAgI — Senator Ted Cruz (@SenTedCruz) May 15, 2019

The public exchange with Cruz is only the most recent high-profile clash involving Thompson over the administration’s Iran policy.

Last month, Reuters reported that Thompson and another senior State Department official, Yleem Poblete, clashed over a State Department report on international compliance on nuclear arms treaties.

Poblete was in charge of drafting the report, but anonymous officials told Reuters that there was concern that the report politicized and slanted assessments on Iran, and it was yanked from the State Department website before reappearing again.

Poblete recently submitted her resignation letter, but has not publicly explained why. Former Rep. Ileana Ros-Lehtinen (R-FL) called Poblete’s leaving a “tremendous loss for our nation’s security.” Cruz tweeted that he was “saddened” by her departure.

During the hearing, Thompson also clashed with Sen. Rand Paul (R-KY), who scolded her for calling Russia’s concerns over the U.S.’s Aegis ashore system “laughable.”

“It sounds to me that you’re not really interested in negotiating with the Russia,” Paul told her. “That’s not what diplomacy is about. Diplomacy is about figuring out what the other side is saying, and not just saying they’re a bunch of crazy, laughable people and we can’t talk to them. That’s a recipe for no diplomacy.”

“You say it’s laughable. Is it something a diplomat should be saying?” he continued. “My advice to you is I wouldn’t say in public that your adversary’s response is laughable. That really goes a long way toward setting back any kind of possible diplomatic solution.”

A senior administration official expressed concern over Thompson’s performance to Breitbart News, asking, “If she can’t handle the Senators how will she handle the Russians?”

The battles come as the president has forged ahead on a dramatically different approach on arms control than the Obama administration, on Iran, Russia, and China.

For example, the Obama administration saw the Iran nuclear deal as its foreign policy legacy; President Trump has pulled out of it and ramped up a pressure campaign on Iran to return to the negotiating table.

The Obama administration continued to stay in the Intermediate-Range Nuclear Forces Treaty despite Russian noncompliance; earlier this year Secretary of State Michael Pompeo announced the U.S. was withdrawing from it. The agreement terminates in August unless Russia comes into compliance.

The Obama administration negotiated the New START Treaty, which limits nuclear warheads and launchers but not new kinds of Russian systems; the Trump administration has not yet made a decision on whether to extend it for another five years past 2021.

President Trump has also voiced recent support for a trilateral arms control agreement that involves Russia and China.

Democrats have criticized such an agreement as unrealistic, since China’s arsenals are far below that of the U.S. and Russia and China would not have an incentive to enter into such an agreement. However, the administration argues that it is important to try, given China’s ambitions to become the world’s superpower by 2050.

Michaela Dodge, research fellow for Missile Defense and Nuclear Deterrence at the Heritage Foundation, explained that the difference between the approaches is that the Obama administration wanted to “lead by example” on arms control, but the Trump administration is more focused on making sure arms control agreements actually advance U.S. national interests.

The Obama administration tried “to create conditions that would eventually allow us to go to nuclear zero, and I think sacrificing in some ways reality of the world in the pursuit of that goal,” she said.

With Trump, she said, “I see less willingness to make compromises in terms of U.S. national security for the sake of general rather unobtainable goals,” she said. “There’s less willingness to cede before you even start negotiations or before you conclude agreements.”