Julian Assange, the WikiLeaks founder, has warned the US government that no matter what it does to try and apprehend Edward Snowden, the revelations he has unearthed on secret digital surveillance of American citizens will see the light of day.

Assange stated pointedly that steps had been taken to foil any US attempt to block publication. "There is no stopping the publishing process at this stage," he said.

Speaking to This Week on ABC news from the Ecuadorean embassy in London, where he is fighting extradition to Sweden to face sexual assault allegations, Assange would not go into details. But he added: "Great care has been taken to make sure Mr Snowden cannot be pressured by any state to stop the publishing process."

Snowden is believed to be holed up in the transit area of a Moscow airport, as he seeks asylum in another country, possibly Ecuador. The former contractor for the National Security Agency has been charged under the 1917 Espionage Act, having leaked classified information on the US government's digital surveillance of phone records, emails and internet communications to the Guardian and the Washington Post.

WikiLeaks has been assisting Snowden in his attempt to avoid capture, providing the 30-year-old with travel expenses and legal counsel and sending advisers to accompany him on his journey from Hong Kong to Moscow earlier this month. Assange said he had offered to help because "we've had some experience in the past with dealing with attacks from the US, with asylum and so on, and I have some personal sympathy for Mr Snowden".

But WikiLeaks has come under criticism from Snowden's father, Lonnie Snowden, who through his lawyer has accused the anti-secrecy organization of using his son to raise money for itself and to prevent Edward Snowden "from doing the right thing" by returning to the US to face charges. Assange told This Week that he had contacted the lawyer to try to "put some of his concerns to rest".

Snowden's predicament, trapped in a legal no man's land between countries, shows no sign of any early resolution. The US government has revoked his passport, making it almost impossible for him to travel on from Russia to any possible final destination. Countries such as Iceland, which Snowden has mentioned as a desired potential safe haven, have made clear that he has to be on their soil before he can claim asylum, creating a legal Catch-22.

Edward Snowden. Photograph: The Guardian/Reuters

The Ecuadorean president, Rafael Correa, told the Associated Press on Sunday that Snowden was "in the care of the Russian authorities" and would not be able to leave Moscow's international airport without his US passport. In a comment that indicated the cautious response of Ecuador to the case, Correa reprimanded Ecuador's consul for issuing Snowden with a letter of safe passage that he is believed to have used to travel from Hong Kong to Russia.

To have done that without consulting the central Ecuadorean government was a "serious error", Correa said. In comments that will not encourage Snowden or his supporters, the Ecuadorean leader added that if Snowden had broken US laws he would have to assume responsibility, adding that the case was "not in Ecuador's hands".

Correa's ambivalent remarks might reflect the fact that he has come under heavy diplomatic pressure from the US to reject Snowden's appeal. On Saturday, Correa said Joe Biden, the US vice president, had contacted him personally by telephone to ask him to dismiss any asylum claim.

The Obama administration shows no sign of wanting to help Snowden find a way out of international limbo. Last week, Barack Obama said: "I'm not going to be scrambling jets to get a 29-year-old hacker." Snowden turned 30 last week.

On Sunday, Nancy Pelosi, leader of the Democratic group in the House of Representatives, told Meet the Press on NBC that in her view "it's pretty good that he's stuck in Moscow airport. That's OK with me – he can stay there."