Sen. John McCain on Thursday warned a former Lockheed Martin vice president that his Pentagon nomination could be in jeopardy unless he answers questions about his potential future role in the defense giant’s foreign military sales.

John Rood, nominee for undersecretary for policy, refused to agree that he would not seek an ethics waiver that would allow him to deal with Lockheed’s overseas weapons sales despite repeated questioning by McCain and Sen. Elizabeth Warren, D-Mass., during his Armed Services Committee confirmation hearing.

McCain said the committee wants a response in writing before voting on Rood, who was nominated by President Trump in October and handled Lockheed’s overseas government relations and marketing. He previously worked at the State Department and sat on the National Security Council under President George W. Bush.

“I suggest you answer the question or you’re going to have trouble getting through this committee,” McCain said.

As a nominee, Rood has already signed an agreement with the Office of Government Ethics that bars him from being involved in Lockheed Martin business for two years and also divested his interest in the company, which is the country’s largest defense contractor. But he declined to say whether he would ever seek a waiver.

“Senator, I am trying to provide a clear answer but those matters that involve particular matters — that is, something that affects the financial health of the company — I’m recused from,” Rood told McCain. “If you’re describing a policy matter such as how the United States should have a relationship with another country in an arms area or cooperation between our air forces, the answer is I would be involved in that and that would not pose a conflict of interest.”

Warren pressed Rood to agree not to seek a waiver on his ethics agreement while working at the Pentagon, in what became an increasingly tense exchange at the confirmation hearing.

“You were responsible for selling Lockheed’s products to other countries. In your new role, you will be responsible for developing defense policy including overseeing policy on foreign military sales to those very same countries,” Warren said. “Will you recuse yourself from policy discussions about the sale of Lockheed products via the foreign military sales and financing programs?”

After three attempts at the question, Warren said she considered Rood’s responses to mean he would not agree.

“How can the American people have any confidence in work that is being done by this nominee is being done on behalf of the American people rather than on behalf of one of the big five defense contractors if we can’t get a straight answer here,” she said.

Lockheed Martin is the nation's largest defense contractor and is the prime defense contractor for the multinational F-35 Joint Strike Fighter program.

Rood said he had signed the same type of ethics agreement required of other nominees in both the Trump and Obama administrations and planned to “live very scrupulously” under the agreement.

“Senator, this is a matter I take very seriously. I’ve consulted with the Defense Department’s chief ethics counselor including as recently as yesterday about that specific matter,” Rood said. “The department has well-established processes in place. I’ve recused from any particular matter involving Lockheed Martin for a period of two years.”

McCain jumped into the exchange several times warning Rood to be more forthcoming and eventually told him the committee will ask for a written response.

“I hope we can clear that up. It is not difficult, you should not be making decisions that are relating to your previous employer or would affect the fortunes of one of them,” McCain said. “So I don’t like your answers, most of us don’t like your answers. We’ll be giving you written questions and I suggest that you answer them thoroughly and completely.”