Glenn Greenwald told Argentina's La Nacion paper that Snowden, who is currently stranded in Moscow, had only sought to alert people that information they thought was private was being exploited by US intelligence agencies.
"Snowden has enough information to cause more damage to the US government in a minute alone than anyone else has ever had in the history of the United States," he told the paper in an interview published on Saturday.
"But that's not his goal," said Greenwald, who published a series of stories in Britain's Guardian newspaper based on top-secret documents about sweeping US surveillance programmes that were leaked by Snowden.
His comments came as Russia waited Sunday for a promised request for asylum from Snowden.
The United States wants the former National Security Agency (NSA) contractor returned to them to face trial over the leaks. Moscow has so far rejected that demand.
Snowden, 30, has been stranded in the transit zone of Moscow's Sheremetyevo airport, after the US withdrew his passport on his arrival from Hong Kong three weeks ago.
Snowden on Friday dramatically summoned Russian activists to his temporary base, to say he wanted to claim asylum in Russia until he could safely travel to Latin America for a permanent sanctuary.
He withdrew an initial request earlier this month after Russian President Vladimir Putin said he would have to stop releasing information embarrassing to Washington if he wanted to stay.
After Snowden made his statement Amnesty International reiterated its support for him and denounced what it described as US government persecution of him.
Human Rights Watch accused Washington of trying to block Snowden's attempts to claim asylum and said that was in violation of his rights under international law.
Representatives from both organisations attended Snowden's presentation.
But on Saturday, officials in Moscow said they were still waiting for Snowden's request.
Mercosur defends asylum rights
Foreign Minister Sergei Lavrov said Snowden would have to submit his application to the Federal Migration Service (FMS), Russian news agencies reported.
The head of Russia's Federal Migration Service (FMS) Konstantin Romodanovsky said Saturday they had received nothing. If they did, he added, it would examined according to the usual procedures.
Washington has reacted sharply to the possibility that Moscow might offer Snowden a safe harbour.
"We would urge the Russian government to afford human rights organisations the ability to do their work in Russia throughout Russia, not just at the Moscow transit lounge," White House spokesman Jay Carney said.
"Providing a propaganda platform for Mr Snowden runs counter to the Russian government's previous declarations of Russia's neutrality," he added.
US President Barack Obama spoke to Putin by telephone Friday on issues including the Snowden affair, the Kremlin and White House both said, but no further details were forthcoming.
The United States has already rebuked China for allowing Snowden to leave for Russia from Hong Kong.
At his meeting with activists, Snowden vowed he did not want to harm the United States.
It was not clear however if this meant he was prepared to stop leaking intelligence in order to stay in Russia.
The leftist governments in Venezuela, Bolivia and Nicaragua have all offered Snowden asylum, but Snowden said that Western governments would prevent him from travelling to the region.
A summit of the Latin American Mercosur trade bloc issued a statement Friday reaffirming the right to asylum and rejecting "any attempt at pressure, harassment or criminalization by a state or third parties".
The bloc, meeting in the Uruguayan capital Montevideo, denounced four European countries who denied airspace to a plane carrying Bolivian President Evo Morales back from Moscow earlier this month.
They apparently suspected that Snowden was on board.
Mercosur leaders said they would recall their ambassadors from Spain, France, Italy and Portugal for consultations in protest at the incident.
In a statement, they rejected "any attempt at pressure, harassment or criminalisation by a state or third parties" in response to a decision to grant asylum.