In a ten-minute interview aired Wednesday morning, NPR’s David Greene asked Wikileaks founder Julian Assange five times to reveal the sources of the leaked information he has published on the internet.

A major tenet of American journalism is that reporters protect their sources. Wikileaks is certainly not a traditional news organization, but Greene’s persistent attempts to get Assange to violate confidentiality was alarming, especially considering that there has been no challenge to the authenticity of the material in question.

In the interview, conducted over Skype, Greene pressed Assange to verify the theory that the 20,000 leaked emails from the Democratic National Committee that Wikileaks published came from Russia.

“Did those hacks that Wikileaks released, did those emails come from Russia?” Greene asked.

“Well we don’t comment as to our sources,” Assange replied. He remains confined in the Ecuadorian embassy in London where he has lived since 2012, despite a U.N. panel’s ruling that he has been “arbitrarily detained.”

Greene brought it up again: “Every cyber expert who’s looked at this has said it’s Russia. Are you telling me that that information did not come to you from Russia?”

Greene was exaggerating: Cybersecurity consultant Matt Tait recently told Politifact that “the consensus that Russia hacked the DNC is at this point very strong, albeit not unanimous.”

Assange replied to Greene: “No cyber expert has said that our emails that we have published have come from Russia, what they have said is that they have looked at some of the hacking of the DNC over the last two years and said that the malware in that hacking appeared to be Russian.”

Greene asked again: “Do you know where these emails came from?”

Assange replied: “Yes, I know where they came from. They came from the DNC.”

NPR’s own ethics handbook urges journalists to respect and protect sources: “As an ethical matter, we would not want to reveal the identity of an anonymous source unless that person has consented to the disclosure. That’s why we take the granting of anonymity seriously.”

NPR’s coverage of James Risen, the New York Times reporter who was pressured by the government to reveal his sources, was more respectful of the obligation to keep promises. Even Terry Gross, the notoriously tough interviewer who hosts NPR member station WHYY’s Fresh Air, did not ask Risen to reveal his sources.

Mark Memmott, NPR supervising editor for standards and practices, told The Intercept in an email: “It’s our job to ask people — experts, politicians, CEOs and even other journalists — where they’re getting their information. We should always be checking the credibility of our sources, no matter who they are. Mr. Assange was free to answer or not.”

Later in the Assange interview, Greene asked again: “Do you know the source that provided them to you?”

Assange replied: “We don’t comment on sourcing, because it makes it easier for any investigation.”

Greene began to ask again: “You brought up this question of whether there’s an argument that you’re a threat to national security. There are cyber security experts who say that someone in Russia, perhaps the Russian government, was responsible for getting this information to you. If you indeed –”

But Assange interrupted: “No there aren’t,” he said. “They’re speaking about the hacks of the DNC, not our publications. There’s a difference.”

Greene again: “If the United States government thought that you might have knowledge that a foreign government hacked into a political institution in the United States” — here Assange sighed — “during a presidential election …” Assange cut in: “They haven’t asked.”

Greene also referred to Wikileaks’ “alleged sources in Russia” and “actual sources in Russia.”

Finally, Greene asked why Wikileaks is offering a $20,000 reward for information about the death of Seth Rich, a Democratic National Committee staffer who was shot and killed on July 10 in Washington, D.C.

“Any allegation that someone has been murdered because they are a Wikileaks source, even if it only has a small probability of it being true, is very concerning to us,” Assange said. “We have a perfect record in protecting the identity of our sources and we want to establish quickly exactly what the circumstances were in Seth Rich’s killing.”

“Was he a source of yours?” Greene asked.

Assange replied: “We don’t disclose sources, even dead sources.”

Naomi LaChance was formerly an intern at NPR.