Calling Apple's concerns in the San Bernardino terror investigations a "diversion," the U.S. government on Thursday argued Apple should comply with a court that ordered it to unlock the iPhone of shooter Syed Rizwan Farook.

Investigating agencies retrieved the phone from Farook's black Lexus after he was shot dead in December. Through a court order, Apple's assistance was sought to unlock the device. Apple refused to comply, citing security and privacy concerns.

"The FBI wants us to make a new version of the iPhone operating system, circumventing several important security features, and install it on an iPhone recovered during the investigation," Apple had earlier said. "In the wrong hands, this software - which does not exist today - would have the potential to unlock any iPhone in someone's physical possession."

The company's public opposition set off a debate of privacy and security that saw many tech titans side with Apple. Others, including Bill Gates, opined the company could comply.

In Thursday's brief filed before the U.S. Central District Court of California, government attorneys argued the case was about one device. "As Apple well knows, the Order does not compel it to unlock other iPhones or to give the government a universal 'master key' or 'back door,'" the government said, while maintaining that the phone contained evidence linked to the shootout.

The administration also called Apple's arguments "rhetoric."

"Instead of complying, Apple attacked the All Writs Act as 'archaic,' the Court's Order as leading to a 'police state,' and the FBI's investigation as shoddy, while extolling itself as the primary guardian of Americans' privacy," the DOJ stated. "Apple's rhetoric is not only false, but also corrosive of the very institutions that are best able to safeguard our liberty and our rights."

Setting aside Apple's concerns that compliance in the case could force it to yield to foreign governments, the brief also suggested Apple had made special considerations for China.

"According to Apple's own data, China demanded information from Apple regarding over 4,000 iPhones in the first half of 2015, and Apple produced data 74% of the time," the brief reads. It also claimed that Apple moved data of its Chinese users to Chinese government servers.

Apple responded sharply through its general counsel Bruce Sewell, who called the brief an indictment. "In 30 years of practice, I don't think I've ever seen a legal brief that was more intended to smear the other side with false accusations and innuendo."