WASHINGTON — Democrats took turns Thursday grilling CIA Director Mike Pompeo over how he would stand up to President Donald Trump on foreign policy and and prioritize diplomacy over military options if confirmed as the next U.S. secretary of state.

During Pompeo’s five-hour confirmation hearing before the Senate Foreign Relations Committee, Sen. Bob Menendez, D-N.J., the panel’s ranking member, raised questions about Pompeo's independence, blasting Trump’s "erratic approach to foreign policy" and asking in his opening statement whether Pompeo would "stand up to Trump" when he’s wrong on an issue or if he’ll be a "yes man."

Sen. Bob Corker, R-Tenn., the panel’s chairman, noted that many "strong voices" within the administration had been fired by Trump or had resigned, and wondered whether the CIA director's close relationship with the president "is rooted in a candid, healthy, give-and-take dynamic."

Pompeo, for his part, pushed back at critics who have labeled him hawkish and promised that he would put diplomacy first — though he declined to answer questions about conversations he had with the president and said he would not resign if Trump fired special counsel Robert Mueller, who is leading the investigation into Russia's meddling in the 2016 election as well as possible collusion with the Trump campaign.

He acknowledged how "demoralizing" the diplomatic corps has found the current staffing situation at the State Department, which has been operating with a slew of vacant positions, and said he would not seek more funding or personnel cuts that critics and foreign policy experts have said are endangered national security.

"There’s no one like someone who understands the value of diplomacy and the terror and tragedy that is war like someone who has served in uniform," said Pompeo, who served in the Army and is a graduate of West Point. "It’s the last resort. It must always be so."

He dismissed one Democratic senator's suggestion that Trump is forming a "war Cabinet" with his nomination and the recent appointment of John Bolton as his new national security adviser.

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Pompeo told the committee that he would like to alter the Iranian nuclear deal reached under the Obama administration, but told senators that even if the U.S. does not recertify the agreement by the May 12 deadline, the administration would continue to work with allies after that point to improve the agreement. Although he'd like to modify the deal, Pompeo added that he has not seen evidence that Iran hasn't complied with the deal's requirements.

He also addressed the administration’s goal of North Korean denuclearization. “We have a responsibility to achieve a condition where Kim Jong Un is unable to threaten the United States with a nuclear weapon," he said, though he added that he was “not advocating regime change.”

Pompeo defended Trump's posture toward Russia, adding that he himself would "take a backseat to no one with my views of the threat that is presented to America from Russia." He said that there is "more work to do" in imposing further sanctions against Russia, and agreed that Russia meddled in the 2016 presidential election.

In an exchange with Sen. Cory Booker, D-N.J., Pompeo rejected the idea that he has made anti-Muslim statements in the past.

"My record is exquisite with respect to treating each and every faith with the dignity that they deserved," he said, adding that he has worked closely with Muslim leaders and Muslim countries and would continue to do so as secretary of state.

The confirmation process for Pompeo, 54, comes at a pivotal moment as the U.S. prepares its response to the alleged chemical attack on a rebel enclave near Damascus, Syria, last weekend. President Donald Trump warned Wednesday that airstrikes against Syria were imminent, though the White House said later that all options remained on the table.

In discussing the possibility of military action in Syria, Pompeo said that multiple administrations have determined that the president has authority to act without seeking congressional approval such as in Kosovo, but said that the U.S. would be “better off” if Congress passed a new authorization for the use of military force (AUMF).

"I believe the president has the domestic authority to do that," Pompeo said, about Trump taking unilateral action against the Syrian government.

In 2013, Pompeo, then a member of the House, argued in an op-ed with Sen. Tom Cotton, R-Ark., in favor of Congress voting on a resolution in favor of President Obama's proposed military strike on Syria following a chemical attack at the time in the suburbs of Damascus.

When asked, however, if Trump has authority to strike North Korea, Pompeo said he would not comment on hypothetical situations or complex legal matters.

Pompeo declined to answer Menendez's questions about any conversation he might have had with Trump about former FBI Director James Comey, but said that he was not asserting executive privilege. He repeatedly said that Trump has "never asked me to do anything that I have considered remotely improper."

And Pompeo told Sen. Chris Coons, D-Del., who has sponsored legislation to protect Mueller's position, that he likely wouldn't resign as secretary of state if Trump were to fire Mueller as special counsel. Pompeo declined to comment on that possibility because he said that, as CIA director, he has been a "participant" in Mueller's investigation.

While Republicans largely expressed approval of Trump’s decision to choose Pompeo as the nation’s next top diplomat, he could potentially face an uphill battle to confirmation with the GOP’s narrow 51-49 majority in the Senate. A simple majority is needed to confirm nominees, and Vice President Mike Pence has the ability to cast a tie-breaking vote.

The Senate confirmed Pompeo as CIA director in January 2017, just days after Trump’s inauguration, in a 66-32 vote. He had previously served in the House, representing a Kansas congressional district, from 2011 until 2017.

Pompeo went on a goodwill tour ahead of his confirmation hearing, meeting with several senators and reaching out to all living former secretaries of state, including Henry Kissinger, John Kerry and Hillary Clinton.

Several members of the Democratic caucus have already come out against Pompeo’s nomination, including Sens. Bernie Sanders, I-Vt.; Ron Wyden, D-Ore.; and Brian Schatz, D-Hawaii. Sen. Rand Paul, R-Ky., has also said he opposes the nomination, a worrying sign for Pompeo.