(CNN) House Intelligence Chairman Devin Nunes lashed out at Attorney General Jeff Sessions last week in a letter where he threatened Sessions with a public grilling if he doesn't produce documents about the Russia dossier to the House intelligence committee.

Nunes, who despite stepping aside from directing the House Russia investigation has been leading his own separate investigation, accused Sessions and the FBI of stonewalling him repeatedly in a September 1 letter obtained by CNN . In the letter, he threatened to drag Sessions and FBI Director Christopher Wray before the committee for a public grilling and hold them in contempt of Congress -- a jailable offense -- if they don't hand over the documents.

The House intelligence committee issued a pair of subpoenas last month seeking documentation of whether the FBI or Justice Department used material from the dossier compiled by former British intelligence agent Christopher Steele as part of the federal investigation into possible collusion between the campaign of President Donald Trump and the Kremlin. Nunes also writes that he subpoenaed to discover whether information from the Russia dossier was used in the crafting of applications to conduct surveillance under the Foreign Intelligence Surveillance Act.

In the letter, which was signed only by Nunes and no other members of the House intelligence committee, Nunes explained that he was extending the deadline for responding to the subpoenas to September 14. But he capped it off with a sharp threat.

"If all responsive documents are not produced by the revised deadline, the Attorney General and Director of the FBI (Christopher Wray) shall appear before the committee at 9 a.m. on September 14, 2017 in room HVC-210 of the US Capitol during an open hearing, to explain under oath DOJ's and FBI's unwillingness or inability to comply in full with the subpoenas issued on August 24," Nunes wrote.

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