Holder also indicated that US officials were still seeking to repatriate Snowden, who is currently in Russia on temporary asylum, so he can stand trial on charges of taking and leaking classified documents about surveillance programs.

Despite “ongoing” talks with Russian officials, however, Holder said that “as of now” Moscow was not open to sending Snowden back to the United States for trial.

“Unless information that has not come to my attention is presented to me, what I have indicated in my testimony before Congress is that any journalist who’s engaged in true journalistic activities is not going to be prosecuted by this Justice Department,” Holder told The Washington Post referring to Greenwald.

The top US law enforcement official also sought to dismiss Greenwald’s writings as advocacy journalism.

“I certainly don’t agree with what Greenwald has done,” he added. “In some ways, he blurs the line between advocate and journalist. But on the basis of what I know now, I’m not sure there is a basis for prosecution of Greenwald.”

Greenwald, in turn, welcomed the move but expressed caution. He has previously said he fears detention and possible prosecution if he returns to the United States.

“That this question is even on people’s minds is a rather grim reflection of the Obama administration’s record on press freedoms,” Greenwald told the Post.

“It is a positive step that the attorney general expressly recognises that journalism is not and should not be a crime in the United States, but given this administration’s poor record on press freedoms, I’ll consult with my counsel on whether one can or should rely on such caveat-riddled oral assertions about the government’s intentions.”

Holder indicated that he will decide by mid-January whether to seek the death penalty for Dzhokhar Tsarnaev, if the 20-year-old is convicted over the Boston Marathon bombings.

“I’ve asked people at every layer -- to the extent that they can -- to take a fresh look at it so that I’m getting a bunch of different perspectives and not a repeat of whatever the initial or the latest recommendation is,” Holder said.

The separate recommendations by US Attorney Carmen Ortiz in Boston, a Justice Department review committee, his deputy James Cole and his counselor Channing Phillips will take into account the offenses, the background and age of Tsarnaev, as well as his alleged role in the attacks that killed three people and wounded more than 260 others.

A police officer was also killed in the aftermath of the twin bombings.

“At the end of the day, it’s going to be me with a large stack of paper... sitting at my kitchen table while everybody else in my house has gone to sleep,” Holder said.

“It’s the single most weighty thing I do as attorney general.”