Microsoft and Google may sue US government to allow them to publish user data request from the government after talks with the Justice Department stalled.

The tech giants filed suits in a US federal court in June, arguing a right to make public more information about user data requests made under the auspices of the Foreign Intelligence Surveillance Act (FISA).

The technology giants agreed six times to extend the deadline for the government to respond to the lawsuits, the Microsoft's general counsel, Brad Smith, wrote in a blog post.

"With the failure of our recent negotiations, we will move forward with litigation in the hope that the courts will uphold our right to speak more freely," he posted on the blog.

"To followers of technology issues, there are many days when Microsoft and Google stand apart," Smith said.

"But today our two companies stand together... We believe we have a clear right under the US Constitution to share more information with the public."

The tech sector has been pushing for greater transparency of government data requests as companies seek to shake off the concerns about their involvement in vast secret US surveillance programmes revealed by former spy contractor Edward Snowden.

National security demands

US officials on Thursday said they would begin publishing annual tallies of national security requests for Internet user data, but that step is not enough, according to Smith.

"For example, we believe it is vital to publish information that clearly shows the number of national security demands for user content, such as the text of an email," Smith said.

He argued that, along with providing numbers of requests, disclosures should provide context regarding what is being sought.

"We believe it's possible to publish these figures in a manner that avoids putting security at risk," Smith said.

There has been a wave of legal action since revelations in the media about the PRISM program, believed to collect vast amounts of phone and Internet data as part of efforts to protect national security.

Internet companies have stated they release information only in response to specific court orders, and claim that reports about providing easy access to US authorities are exaggerated.

US authorities insist the surveillance programmes are entirely lawful and have helped thwart dozens of terror attacks.