Facebook founder Mark Zuckerberg says he has called President Barack Obama to "express frustration" over American digital surveillance.
He says in a blog post that the United States government "should be the champion for the internet, not a threat".
Mr Zuckerberg's comments come a day after a report that the US National Security Agency imitated a Facebook server in order to expand its spying capability through malware.
Mr Zuckerberg said in September that the US "blew it" on internet spying. He now says "it seems like it will take a very long time for true full reform".
"When our engineers work tirelessly to improve security," he says in his blog, "we imagine we're protecting you against criminals, not our own government.
"The US government should be the champion for the internet, not a threat. They need to be much more transparent about what they're doing, or otherwise people will believe the worst."
The NSA's activities were leaked by a former contractor for the agency, Edward Snowden, last year. His leaks have pointed to the NSA collecting phone records, tapping fibre-optic cables that carry global communications and hacking networks.
According to the documents, the agencies had "backdoor" access to the servers of nine major technology companies including Microsoft, Yahoo, Google, Facebook, PalTalk, AOL, Skype, YouTube and Apple.
All the companies named have denied their involvement.
Since the revelations, Facebook has teamed up with Google, Apple, Microsoft, Twitter, AOL, LinkedIn and Yahoo to form an alliance called Reform Government Surveillance.
The group has called for "wide-scale changes" to US government snooping.
Earlier this week, Mr Snowden told a conference that mass surveillance conducted by the US and other governments was "setting fire to the future of the internet".