President Donald Trump’s nominee to lead the Department of Defense told a Senate committee on Tuesday that he would not agree to recuse himself, if confirmed, from decisions affecting the defense contracting giant for which he previously served as a top Washington lobbyist.

In a contentious exchange with Sen. Elizabeth Warren (D-MA), a Democratic candidate for the 2020 presidential nomination, acting Pentagon chief Mark Esper said he would not commit to steering clear of matters involving Raytheon, his former employer and the nation's third largest military contractor.

“On the advice of my ethics folks at the Pentagon, the career professionals, no, their recommendation is not to,” Esper told Warren at a Senate Armed Services Committee hearing on Tuesday. “The belief is the screening process I have in place, all the rules and regulations and laws, are sufficient.”

Esper previously committed to such a recusal when he assumed a post as Secretary of the Army. But the window for recusal was just two years, and expires in November. Trump’s last acting defense secretary, former Boeing executive Patrick Shanahan, faced a similar situation, but pledged during confirmation hearings to voluntarily extend his recusal for the duration of his time atop the Pentagon.

“Senator, I can’t explain why he made that commitment,” Esper told Warren. “He has a different professional background than I do.”

In a June memo detailing his ethics obligations, Esper noted that even absent such an obligation, he would still be barred from taking any action as defense secretary that would have a “direct and predictable effect” on Raytheon’s bottom line.

But Esper added in the same memo that he would be free to seek a waiver to those ethics rules for any decision that is “so important that it cannot be referred to another official.” The Trump administration has granted dozens of such waivers to various laws and regulations limiting actual or perceived conflicts of interest.

Esper told Warren that he has not sought such a waiver, but left the door open to doing so in the future. “I’m going to continue to abide by the rules and regulations,” he said. He also declined to commit to refraining from taking a position at Raytheon for four years after leaving the Defense Department.

“The American people deserve to know that you’re making decisions in our country’s best security interests, not in your own financial interests,” Warren declared. “You can’t make those commitments to this committee, that means you should not be confirmed as Secretary of Defense.”

Esper shot back at what he called Warren’s “presumption" that "for some reason anybody who comes from the business world or the corporate world is corrupt.”

“At the age of 18, I went to West Point and I swore an oath to defend this Constitution,” Esper said. “I embraced the motto of duty, honor, and country. And I have lived my life in accordance with those values ever since then. I went to war for this country. I served overseas for this country.”

Esper is vying to lead a Pentagon dogged by recent conflict of interest allegations among its top leadership. Before Shanahan resigned over years-old reports of domestic violence in his home, he faced similar allegations involving his former employer, Boeing. An inspector general report cleared Shanahan of any wrongdoing.

“I’ve stepped down from jobs that paid me well more than what I was making anywhere else,” Esper said at Tuesday’s hearing. “And each time it was to serve the public good and to serve the men and women of our armed forces.”

Warren attempted to press Esper on the issue before her time expired. She ended with an exasperated “this is outrageous” as Armed Services Committee Chairman Sen. Jim Inhofe (R-OK), who briefly acquired Raytheon stock last year days after pushing for a huge hike in defense spending, cut off the line of questioning.