President Trump on Monday extolled House Intelligence Committee Chairman Devin Nunes (R-Calif.) as “a very courageous man” as they attended the swearing in of Trump’s new CIA director, Gina Haspel.

“A very courageous man — he’s courageous,” Trump said as he recognized Nunes’s attendance at the ceremony at CIA headquarters in Langley, Va. “Thank you very much, Devin, for being here, appreciate it.”

The praise comes as Nunes remains in a standoff with Justice Department officials over documents related to the counterintelligence investigation into Russian interference in the 2016 presidential election and possible collusion with Trump’s campaign.

Recent reports have indicated that a longtime U.S. intelligence source assisted the investigation now overseen by special counsel Robert S. Mueller III. The Washington Post reported Friday that the source, a retired American professor, had contacts with three Trump advisers during the 2016 campaign.

Late last month, Nunes issued a subpoena to the Justice Department seeking all documents related to the professor. In resisting the request, department officials have said that exposing the source or the source’s work could put him and his contacts in danger and jeopardize international intelligence partnerships.

Law enforcement officials consider the informant’s identity so sensitive that the FBI had been working over the past two weeks to mitigate the potential damage if his name were revealed, according to several people familiar with the matter.

Trump and his allies have seized on the informant’s role to claim that the FBI spied on his campaign during President Barack Obama’s administration. There is no evidence to indicate an intelligence source was embedded within the campaign, however, as Trump has suggested.

On Sunday, under pressure from Trump, the Justice Department asked its inspector general to assess whether political motivation tainted the FBI investigation into ties between Russia and Trump’s campaign.

Matt Zapotosky contributed to this report.