According to people working with Snowden, he remains somewhere in Hong Kong.
The former intelligence contractor leaked top secret National Security Agency documents on U.S. surveillance programs to The Guardian newspaper.
"Of course I'm concerned with the fate of my source, and somebody who I think did a great public service," said Glenn Greenwald, columnist for the Guardian. "At the same time, he's a very rational, smart, intelligent person who made this choice with full recognition of what he was likely bringing upon himself."
Government contractor Booz Allen Hamilton says it fired Snowden, an employee of the firm for less than three months, on Monday for violating the company's code of ethics.
"News reports that this individual has claimed to have leaked classified information are shocking, and if accurate, this action represents a grave violation of the code of conduct and core values of our firm," the company said in a statement.
Greenwald says Snowden wanted Americans to know their government is eavesdropping on them, and says more significant revelations will be published.
"We have more documents that we intend to make public by writing about them journalistically," Greenwald said. "Whether (Snowden) has additional documents that he hasn't given us is something I can't answer for him."
Greenwald says one program collects hundreds of millions of phone records, while another collects emails and the electronic activities of foreign nationals who use providers like Microsoft and Apple.
In an exclusive interview with ABC News, House Speaker John Boehner called Snowden a traitor for leaking classified information.
"The president outlined last week that these are important national security programs to help keep Americans safe and give us tools to fight the terrorist threats that we face," Boehner said. "The disclosure of this information puts Americans at risk."
There is growing support Snowden: An online petition asking the White House for a pardon has received over 47,000 signatures already, and others have offered to set up his legal defense fund.
Dogged by fear and confusion about sweeping spy programs, intelligence officials sought to convince House lawmakers in an unusual briefing Tuesday that the government's years-long collection of phone records and Internet usage is necessary for protecting Americans - and does not trample on their privacy rights.
Russia's foreign minister says his nation hasn't received an asylum request from the American who has identified himself as the person who leaked details of a secret National Security Agency surveillance program.
Russian Foreign Minister Sergey Lavrov is visiting Brazil. He said Tuesday that if a request arrives from Edward Snowden, "we will examine that request."
The Associated Press and ABC News contributed to this report.