Google, Facebook Inc, Microsoft Corp and about a dozen other internet companies will file a joint legal brief asking a judge to support Apple Inc in its encryption battle with the US government.
They will outline their rationale for supporting Apple in an amicus brief on Thursday to the Riverside, California, federal judge who will rule on Apple's appeal of a court order that would force it to unlock an iPhone associated with last December's shootings in San Bernardino.
Privacy advocacy groups The American Civil Liberties Union, Access Now and the Wickr Foundation filed briefs on Wednesday in support of Apple before Thursday's deadline set by Judge Sheri Pym.
Salihin Kondoker, whose wife Anies Kondoker was injured in the attack, also wrote on Apple's behalf, saying he shared the company's fear that the software the government wants Apple to create to unlock the phone could be used to break into millions of other phones.
The fight between Apple and the government became public last month when the Federal Bureau of Investigation obtained a court order requiring Apple to write new software and take other measures to disable passcode protection and give access to the iPhone that was used by San Bernardino gunman Rizwan Farook.
Apple pushed back, arguing such a move would set a dangerous precedent and threaten customer security.
The clash has intensified a long running debate over how much law enforcement and intelligence officials should be able to monitor digital communications.
Law enforcement officials have said that Farook and his wife, Tashfeen Malik, were inspired by Islamist militants when they shot and killed 14 people and wounded 22 others last December at a holiday party.
Farook and Malik were later killed in a shootout with police and the FBI said it wants to read the data on Farook's phone to investigate any links with militant groups.
