WASHINGTON -- Aiming to quell concerns before what is likely to be a narrow confirmation vote, Secretary of State-designate Mike Pompeo vowed on Thursday to ramp up efforts against Russia in "each place we confront them." But he ducked and dodged when asked whether he supports President Donald Trump's pounding criticism of the federal investigation into Russian meddling in the 2016 election.

Pompeo, now Trump's CIA chief, tread carefully when confronted with several of the president's controversial and undiplomatic statements, focusing instead on his plans to rebuild a depleted agency and restore its influence. Pompeo suggested he did not share all the president's views -- including his skepticism about Russia's interference.

"I take a back seat to no one" when it comes to standing up to Russia, Pompeo said.

However, when asked if he would resign if Trump moved to scuttle the probe by firing special counsel Robert Mueller or the deputy attorney general to whom he reports, he said no.

Pompeo's nomination faces stiff opposition from a handful of Republicans and many Democrats as well as supporters of the Iran nuclear deal, environmentalists and minority rights groups, and his testimony before the Senate Foreign Relations Committee appeared designed to blunt their criticism. The CIA chief told senators that he has been miscast as a "hawk" despite previous comments savaging the Iran accord and hinting at regime change in North Korea. He maintained he wants to improve the Iran deal and would continue efforts to do so even if Trump withdraws from it as he has threatened.

In his testimony, Pompeo confirmed for the first time publicly that he's been interviewed by the team of special counsel Mueller, who is investigating possible ties between Russia and Trump's presidential campaign as well as possible obstruction of justice issues. But he wouldn't answer questions about the contents of the interview, arguing it would be improper since, as CIA director in charge of overseas intelligence gathering, he has been a "participant" in Mueller's probe.

Under questioning, he said he would be unlikely to resign as secretary of state if Trump were to fire Mueller. Lawmakers are concerned the president may seek Mueller's ouster to try to shut down the investigation, and the White House has said it believes Trump does have the authority to fire him if desired.

"My instincts tell me no," Pompeo said about possibly resigning. "My instincts tell me my obligation to continue to serve as America's senior diplomat will be more important in times of domestic political turmoil."

Throughout the hearing, he drew a sharp contrast between himself and Tillerson, the former CEO of ExxonMobil who Trump unceremoniously fired last month. He lamented the "demoralizing" vacancies at the top echelons of the department during Tillerson's brief tenure and said he planned to fill those vacancies.

He cast his close connection to Trump as an advantage that would help him restore the significance of the department.

"My relationship with President Trump is due to one thing: We've demonstrated value to him at the CIA. So, in turn, he has come to rely on us," Pompeo said. "I intend to ensure that the Department of State will be just as central to the president's policies and the national security of the United States."

His remarks before the committee were the first chance for lawmakers and the public to hear directly from the former Kansas congressman about his approach to diplomacy and the role of the State Department, should he be confirmed. Pompeo's views on global issues are well known -- he was questioned extensively by senators for his confirmation to run the CIA -- but Democratic senators have raised questions about his fitness to be top diplomat, given his hawkish views and past comments about minorities.

Sen. Cory Booker, D-N.J., took Pompeo to task over for saying previously that Muslims have a special obligation to denounce extremism and for his longstanding position that gays should not be able to marry.

"I continue to hold that view," Pompeo said of gay marriage, though he declined repeatedly to answer whether he believes gay sex is a "perversion." Pompeo said that his record at the CIA and elsewhere proves he treats everyone equally and with respect, regardless of religion, gender or sexual orientation.

He sought to pre-empt concerns about Trump's apparent unwillingness to challenge Russian President Vladimir Putin directly. He said a long list of punitive actions taken under Trump show the U.S. takes the threat from Russia seriously, adding that "we need to push back in each place we confront them," including the economic and cyber arenas.

An avowed opponent of the Iran nuclear deal, Pompeo said he'd work immediately if confirmed to "fix" the agreement that Trump has threatened to abandon if it's not strengthened. Pompeo wouldn't say explicitly if he'd advocate a withdrawal if there's no fix by Trump's May 12 deadline, suggesting there could be an extension if significant progress was being made by then. Still, he affirmed that he won't support staying in over the long term unless more restrictions are placed on Tehran.

"If there's no chance that we can fix it, I will recommend to the president that we work with our allies to achieve a better outcome and to achieve a better deal," Pompeo said.

To the dismay of some Democratic lawmakers, Pompeo equivocated when asked about climate change -- acknowledging it is occurring but saying only that it's "likely" that humans are contributing to it. Still, although Trump has announced the U.S. is pulling out of the Paris global climate agreement, Pompeo said the State Department should be involved in global efforts to address global warming.

------

Associated Press writer Matthew Pennington contributed to this report.