Grigory Rodchenkov, the main whistleblower who exposed the Russian doping scandal, has met with members of a United States Federal Government Agency to discuss sporting and wider political issues.
Wearing a mask to hide his identity, the former Moscow Laboratory director spoke on issues including the "threat posed by Russia to the United States, corruption in international sports bodies, and how the United States can contribute to the international effort to counter doping fraud".
He was meeting with Senators Ben Cardin and Cory Gardner and House of Representatives member Sheila Jackson-Lee - three representatives of the Commission on Security and Cooperation in Europe, also known as the US Helsinki Commission.
Rodchenkov's "precarious circumstances" in the US were also discussed after he fled from Russia more than two years ago.
"Dr. Rodchenkov's story is yet another example of the Kremlin's willingness to flout international rules and standards," said Cardin afterwards.
"It is deplorable that he must continue to fear for his life and was forced even to wear a ski mask in our meeting today to protect his appearance.
"Yet in light of the recent nerve gas attack in England made in retaliation against Sergei Skripal, this appears totally, tragically justified.
"I am impressed and inspired by Dr. Rodchenkov's bravery.
"I will continue to speak out about the fundamental human rights of the Russian people, and push the administration to do more to push back on Russia's attacks on our norms and values."
Rodchenkov, the main subject of Oscar winning documentary Icarus, was at the centre of what the International Olympic Committee described as a "systemic manipulation" of the anti-doping system at the Sochi 2014 Winter Olympic Games.
His information formed the basis of the World Anti-Doping Agency-commissioned McLaren Report and set into motion a chain of events culminating in Russian athletes being forced to compete in a neutral team at last month's Winter Olympics in Pyeongchang.
"Dr. Rodchenkov is a courageous individual whose whistleblowing has strengthened the global fight against corruption in international sports and elsewhere," added Jackson-Lee.
"It was a pleasure to meet him in person.
"Whistleblowers are a fundamental element of society based on the rule of law.
"His story deserves to be told and emulated again and again."
The Helsinki Commission is billed as a US Government agency that "promotes human rights, military security, and economic cooperation in 57 countries in Europe, Eurasia, and North America".
The meeting is bound to lead to more criticism in Russia, where Rodchenkov is viewed largely as a traitor and as an agent of the US authorities.