WASHINGTON — Donald Trump’s pick to run the CIA took a tough stand against Russia on Thursday, distancing himself from the president-elect, who wants to warm relations with Moscow.

Rep. Mike Pompeo, a four-term conservative Kansas Republican, spoke at his confirmation hearing before the Senate intelligence committee amid a testy standoff between Trump and the spy community over Russian activities during the president election.

“Russia has reasserted itself aggressively, invading and occupying Ukraine, threatening Europe and doing nothing to aid in the defeat of ISIS,” Pompeo said, referring to Islamic State militants.

If confirmed, Pompeo would take the helm of the CIA in what he said was the “most complicated threat environment the United States has faced in recent memory.”

Pompeo was a vocal member of the partisan House committee set up to investigate the deadly attack on a U.S. diplomatic post in Benghazi, Libya, in 2012, which occurred while Hillary Clinton was secretary of state. He told the committee that he understands that as CIA director he would have to make the transition from a partisan, policymaking lawmaker to an objective intelligence collector.

“I have spent the majority of my life outside politics – as a U.S. Army cavalry officer, litigator and head of two manufacturing businesses,” Pompeo said. “Returning to duty that requires hard work and unerring candor is something that is in my bones.”

As CIA director, Pompeo could be caught in the role of mending relations between Trump and intelligence officials. Trump has for the most part been dismissive of intelligence agencies’ findings that Russia, specifically President Vladimir Putin, interfered in the 2016 U.S. election with the goal of getting Trump elected. The CIA is one of three main intelligence agencies that came to that conclusion.

On Wednesday, Trump acknowledged Russia was responsible for hacking but speculated that intelligence agencies might have leaked to news organizations details about a classified briefing with him that included unsubstantiated allegations about his ties to Russia.

On other issues, Pompeo said Iran has become an “even more emboldened and disruptive player in the Middle East.” He said North Korea has dangerously accelerated its nuclear and ballistic missile capabilities. And he called the conflict in Syria a tragic humanitarian catastrophe that has led to the rise of extremism and sectarianism and has destabilized the Middle East and Europe.

Pompeo has been critical of the Obama administration’s nuclear deal with Iran, which granted Tehran sanctions relief for rolling back its nuclear weapons program.

“While I opposed the Iran deal as a member of Congress, if confirmed, my role will change,” Pompeo said. “I will lead the agency to aggressively pursue collection operations and ensure analysts have the time, political space and resources to make objective and sound judgments.”

Pompeo graduated first in the Class of 1986 at the U.S. Military Academy at West Point. He served in the Army at a time when the Soviet Union was America’s main adversary. As a member of the House Intelligence Committee, Pompeo traveled widely and met many intelligence professionals.