Edward Snowden, the former National Security Agency contractor that exposed the agency's most closely held secrets, said today that while returning to the U.S. would be the "best resolution" for everyone, it's "not possible" now because he does not believe he can get a fair trial.

Charged in the U.S. with espionage-related crimes and living quietly in Russia, Snowden answered Twitter questions today in an online Q&A. When CNN's Jake Tapper asked under what conditions Snowden would return to the U.S., the 30-year-old said the nearly 100-year-old Espionage Act, under which he is charged, "forbids a public interest defense."

"This is especially frustrating, because it means there's no chance to have a fair trial, and no way I can come home and make my case to a jury," he said.

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In a Wall Street Journal Op Ed Tuesday, attorney Jesselyn Radack, who has represented government whistleblowers in the past and has had contact with Snowden, argued similarly that it's a "fantasy" to think Snowden would be able to mount a solid defense in a fair trial due to Espionage Act-related government restrictions.

Earlier today U.S. Attorney General Eric Holder said that if Snowden wanted to return to the U.S. and enter a guilty plea, the Justice Department would "engage with his lawyers."

"Of course if Mr. Snowden's lawyers informed us their client was prepared to take accountability by pleading guilty to the charges filed against him, we would engage with his lawyers on that, as we would with any other defendant," a Department of Justice spokesperson echoed later.

Last June Holder wrote a letter to his Russian counterpart in which he promised the U.S. would not torture or execute Snowden - an attempt to refute the grounds upon which Snowden originally made his asylum plea. At the time, Holder said that should Snowden return, he would be provided all the protections the law allows.

Today's Q&A was the second conducted by Snowden since he revealed himself to be the source in a seemingly never-ending stream of reports about the NSA's vast foreign and domestic espionage operations. Snowden is currently living in Russia under temporary asylum, having fled his contractor job at the NSA in Hawaii first for Hong Kong and then for Moscow.

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