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Apple is not backing down.

CEO Tim Cook on Monday urged the US government to drop its demands for his company to create a backdoor into an iPhone tied to a terrorist attack. Apple contends that such a breach of security could not be contained and would expose countless iPhone users to unreasonable risks.

Instead, Cook said in an email to employees Monday, he wants Congress to form a commission to "discuss the implications for law enforcement, national security, privacy and personal freedoms."

Cook has been in the spotlight over the past week for standing up to government investigators. In his email, he thanked employees for their support and detailed his stance. Apple also published a Q&A on its website to address customers' questions about the issue.

"Apple is a uniquely American company," Cook said in the email. "It does not feel right to be on the opposite side of the government in a case centering on the freedoms and liberties that government is meant to protect."

Leaders of the House Energy and Commerce Committee on Monday invited Cook and FBI Director James Comey to appear before the committee "to discuss the issues surrounding encryption -- specifically when privacy and national security issues are raised." Apple didn't immediately say whether Cook plans to attend.

For more than a decade, the tension between privacy and national security has run high over how technology can be used to investigate and anticipate threats. The current standoff between Apple and the FBI also turns up the heat on the simmering battle over encryption -- the technology that scrambles information to prevent unauthorized readers from seeing it -- between Washington and Silicon Valley.

Last week, a federal judge ordered Apple to assist the FBI in unlocking an iPhone 5C used by Syed Farook, one of two terrorists who killed 14 people at a party in San Bernardino, California, in December. The government wants Apple to create a new variant of its iOS software to grant investigators access to data on the device, but Cook warned that such a version of iOS would create, for the first time, a backdoor into all of Apple's encrypted devices.

The government is using the All Writs Act, which was signed into law by President George Washington in 1789, to try to force Apple to change its software. The act helped establish the judiciary system in the US, giving federal courts the power to issue orders, which were known as "writs" at the time.

The company has until Friday to respond to the court order, and a hearing is set for March 22 in US District Court for the Central District of California in Riverside. Apple has said it will fight the government's request all the way to the Supreme Court, if necessary, because it means creating a "master key" for all phones that would make them less secure.

The FBI disputes that view.

"The relief we seek is limited and its value increasingly obsolete because the technology continues to evolve," Comey said in a statement late Sunday. "We don't want to break anyone's encryption or set a master key loose on the land."

Face-off

Over the weekend, Apple and the FBI traded barbs over the series of events that led to the court battle. The issue could have been avoided, Apple said, if the FBI had connected Farook's iPhone 5C to a familiar Wi-Fi network and had it create a new backup on Apple's iCloud service. But the County of San Bernardino, at the behest of the FBI, had reset Farook's iCloud password.

"Even if the password had not been changed and Apple could have turned on the auto-backup and loaded it to the cloud," the FBI said Sunday, "there might be information on the phone that would not be accessible without Apple's assistance as required by the All Writs Act order, since the iCloud backup does not contain everything on an iPhone."

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Cook on Monday called the government's request a "dangerous precedent that threatens everyone's civil liberties" and said that complying with the court order would "roll back data protections to iOS 7," which hit the market in September 2013. With iOS 8, released the following year, Apple started encrypting everything on iPhones, making personal data more secure but also preventing the company from circumventing passcodes to pull data from phones to comply with search warrants, as it had done in the past.

"We all know that turning back the clock on that progress would be a terrible idea," Cook said Monday.

He added that if Apple created a new version of iOS for the government, it couldn't be completely destroyed after use in the San Bernardino and instead could be used over and over again.

"Law enforcement agents around the country have already said they have hundreds of iPhones they want Apple to unlock if the FBI wins this case," Cook said.

Americans have been divided over whether Apple should do as the FBI has asked. Donald Trump, the billionaire and frontrunner for the Republican nomination for president, called for a boycott of Apple's products until it complies with the court order. The family of a UK terrorist attack victim also has criticized Apple.

But in his email Monday, Cook said he has received supportive "messages from thousands of people in all 50 states." One email from a 13-year-old app developer "thanked us for standing up for 'all future generations,'" Cook said. "And a 30-year Army veteran told me, 'Like my freedom, I will always consider my privacy as a treasure.'"

Full text of the email to Apple employees from Cook: