General Alexander, director of the National Security Agency and U.S. Cyber Command, gestures while speaking to reporters during the Reuters Cybersecurity Summit in Washington

National Security Agency chief Gen. Keith Alexander will address the House intelligence committee on Tuesday in a rare public hearing that could shed new light on the scope of the federal government’s classified phone and Internet surveillance programs.

The session involving two of Washington’s most secretive bodies comes as an NSA leaker, former contractor Edward Snowden, threatens to reveal more government secrets from his hiding spot in Hong Kong.

Alexander has already gone to Capitol Hill several times since Snowden revealed details earlier this month about the government programs — to discuss the agency’s budget and meet privately with congressional members.