Deputy Attorney General Rod Rosenstein, who has come under fire by President Trump and Republican lawmakers, responded on Tuesday to the conservative House Freedom Caucus drafting articles of impeachment against him by warning that he will not be extorted.

The caucus move represented increasing tension between the Department of Justice and conservative lawmakers about the scope and continuity of special counsel Robert Mueller’s investigation into possible collusion between Trump and Russian officials during the presidential campaign.

“They can’t even resist leaking their own drafts,” Rosenstein said at an event at the Newseum on Tuesday afternoon. “I just don’t have anything to say about documents like that, that nobody has the courage to put their name on and that they leak in that way.”

He also said: “I can tell you that there have been people that have been making threats against me privately and publicly for some time, and I think they should understand by now the Department of Justice is not going to be extorted.”

The Washington Post reported that the draft articles, which had been referred to as a "last resort," were created after members have been attempting to get documents from the Department of Justice about FBI surveillance of the Trump campaign as well as information about the probe into Hillary Clinton's email server.

“My frustrations about their inability to respond to simple requests could warrant further action,” Freedom Caucus chairman Rep. Mark Meadows (R-NC) told the Post.

A spokesperson for the caucus did not respond to a request for comment from The Daily Beast about Rosenstein's remarks.

Rosenstein also specifically addressed the caucus' concern about obtaining a FISA warrant.

"There's a lot of talk about FISA application and many of the people I see talking about it seem not to recognize what it is. A FISA application is actually a warrant, just like a search warrant," Rosenstein said. "In order to get a FISA search warrant, you need an affidavit signed by a career federal law enforcement officer who swears that the information in the affidavit is true and correct to the best of knowledge and belief. And that is the way we operate, and if that is wrong, sometimes there is, if you find there is anything incorrect in there, that person is going to face consequences."