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By Josh Lipton, CNBC

Apple has been given more time to respond to a Department of Justice order to assist the Federal Bureau of Investigation in unlocking an iPhone used by the perpetrators of last year's terror attacks in California, sources said Thursday.

Apple's response in court will now be due February 26 instead of Tuesday, the sources told CNBC.

Federal Magistrate Judge Sheri Pym — who on February 16 granted the DOJ's request for an order demanding Apple assist the FBI — had originally given the company 5 business days to respond.

A U.S. magistrate's order that Apple help the FBI access an iPhone belonging to one of the San Bernardino terrorists is "chilling" and is essentially asking the U.S. tech giant to "hack" its own users, Chief Executive Tim Cook said earlier this week.

In a letter to customers on Wednesday, Cook said he opposes a "dangerous" court order.

"The United States government has demanded that Apple take an unprecedented step which threatens the security of our customers. We oppose this order, which has implications far beyond the legal case at hand," Cook said.

Josh Lipton, CNBC

Josh Lipton is CNBC's technology correspondent, working from CNBC's Silicon Valley bureau. Lipton joined CNBC in January 2013 as an on-air markets reporter located at CNBC Global Headquarters in Englewood Cliffs, N.J.

Previously, Lipton was the markets editor for Bloomberg Television where he was responsible for all markets coverage, working with Bloomberg's team to develop reports on stocks, bonds, currencies and commodities. He also appeared weekdays on "In the Loop with Betty Liu."