Guardian newspaper columnist Glenn Greenwald said Sunday he doesn't know where Edward Snowden -- the man who revealed information about the U.S. government's sweeping surveillance efforts -- is ultimately headed after Snowden's departure from Hong Kong on Sunday.

"Where's he's ultimately headed is unknown," Greenwald said on NBC's "Meet The Press." He later added: "He's my source for these stories; I'm not going to talk about where I think he is going."

Greenwald first reported on the National Security Agency's sweeping phone record surveillance program.

Snowden left Hong Kong on Sunday, and reportedly landed in Moscow. Reports indicate he may ultimately be headed for Cuba and Venezuela. Meanwhile, Ecuador's foreign minister tweeted Sunday afternoon that his government had received a request for asylum from Snowden. Cuba and/or Venezuela could be stopping points on the way to Ecuador.

Updated at 2:52 p.m.