Former National Security Adviser Gen. H.R. McMaster, Ret., told Fox News Wednesday that the Biden administration should be under "no illusions" as to the ruthlessness of Russian President Vladimir Putin's casual use of hostage-taking as a means to conduct foreign policy.

McMaster told "The Story" that Biden likely had the captivity of Americans Trevor Reed and Paul Whelan at the top of his list to discuss with the ex-KGB agent who has led Russia nearly continuously since 1999:

"What we need is constant advocacy for the release of what are essentially hostages. This is a regime under Putin, who engages in hostage-taking as an arm of their foreign policy. He also uses criminal networks routinely," said McMaster, who was the National Security Advisor under President Donald Trump.

He said Putin should be held to account not simply for recent cyberattacks on critical U.S. infrastructure that reportedly came from within the country, but also for his use of organized crime syndicates to further the Russian Federation's policy interests.

For his part, Putin appeared warm to a prisoner "swap" with the U.S., though the names considered at the top of the Russian president's list raised eyebrows stateside.

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The Kremlin indicated an interest to potentially trade captive Americans for Viktor Bout, an arms dealer dubbed "The Merchant of Death," and drug smuggler Konstantin Yaroshenko.

Reed, a former Marine who was previously posted at Camp David and elsewhere during the Obama administration, was arrested in Russia during an alleged inebriated altercation following a private party. Reed was in Russia to visit his girlfriend.

Putin used an expletive during an NBC News interview this week to describe Reed at the time of his arrest, and Fox News previously reported that the U.S. citizen was initially taken to a police precinct to sober up, but things went downhill after the FSB – the successor to the KGB – discovered his military history. 

"This is why we should be under no illusions about the nature of the Kremlin under Putin's leadership. This is a leader who is ruthless. A leader that will take innocent people hostage for coercive purposes," McMaster added Thursday.

Biden appeared to become angry with a female reporter who shouted a question to him about his confidence that Putin would indeed change his malign behavior.

The reporter, identified as Kaitlan Collins of CNN, pressed him on the subject, eliciting the Delaware Democrat to curtly respond in part, "I'm not confident he'll change his behavior: What in the hell -- what do you do all the time?"

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Collins noted Putin's behavior has not changed despite past overtures by the U.S. and others and said he continues to downplay human rights abuses. "If you don't understand that, you're in the wrong business," Biden told Collins, before finally walking away.

McMaster compared the captivity of Reed and Whelan to the predicament of Michael Kovrig and Michael Spavor – two Canadian nationals to date denied due process and who are languishing in a Chinese prison for what is now their third year behind bars.

"I think it's time and I hope that president Biden succeeds in rallying the free world to take action," McMaster said.