The U.S. Justice Department urged a federal judge in California Thursday to stick with her original order directing Apple to help the FBI open a locked iPhone used by one of the San Bernardino attackers.

"The government and the community need to know what is on the terrorist's phone and the government needs Apple's assistance to find out," federal prosecutors said in responding to Apple's motion to vacate the order.

Magistrate Judge Sheri Pym last month ordered Apple to disable security functions on the phone that would allow the FBI to enter thousands of different combinations of numbers in an effort to guess the security passcode and open the phone.

The smartphone maker responded that the order would violate the First and Fifth Amendments, and said disabling the phone's security would require writing new software, which it dubbed "GovtOS." That effort would take as many as ten engineers a period of up to a month of dedicated work, it said.

Related: Why Are Apple and the FBI Battling Over an iPhone?

Apple, one of the world's most valuable companies, said it would also need to conduct quality assurance and other testing and that the entire process would need to be thoroughly documented. Apple and security experts said that the technology would almost certainly be stolen by hackers or demanded by foreign governments once created, potentially putting many other iDevices at risk.

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But the government lawyers said Thursday that Apple is fully capable of complying with the order.

"By Apple's own reckoning, the corporation — which grosses hundreds of billions of dollars a year — would need to set aside as few of six of its 100,000 employees for as little as two weeks."

Any burden on the company, the government said, "is the direct result of Apple's deliberate marketing decision to engineer its products so that the government cannot search them, even with a warrant."

If the government's request is granted, Apple said, "what is to stop the government from demanding that Apple write code to turn on the microphone in aid of government surveillance, activate the video camera, surreptitiously record conversations to track the phone's user? Nothing.”

But the Justice Department said what it seeks is modest, applying to a single iPhone, and would not create a "master key" or a "back door."

Related: FBI Wants to 'Turn Back the Clock' on iPhone, Apple Software Chief Says

"Apple deliberately raised technological barriers that now stand between a lawful warrant and an iPhone containing evidence related to the terrorist mass murders of 14 Americans. Apple along can remove those barriers," the Justice Department filing said.

The Justice Department said that Apple had portrayed the FBI's work in the case as "shoddy." The two sides have made their arguments to the public in editorial pages, press statements and congressional hearings in recent weeks.

"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: the courts, the Fourth Amendment, longstanding precedent and venerable laws, and the democratically elected branches of government."

Apple general counsel Bruce Sewell called the Justice Department filing a "cheap shot brief" in a conference call with reporters on Thursday, saying that it read "like 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 and less intended to focus on the real merits of the case," Sewell said.

Industry leaders including Google, Facebook, AT&T, and Microsoft are among companies that have filed court briefs backing Apple in the case. The government has received support from groups including the Federal Law Enforcement Officers Association and the National Sheriffs' Association, as well as six family members of victims in the San Bernardino shooting.

A lawyer with the American Civil Liberties Union said Thursday that the government’s arguments are misleading, and a decision against Apple would set a precedent.

"The government tries to characterize this case as about one phone, rather than acknowledging that the precedent could be used over and over to force technology companies to undermine their security measures for law enforcement purposes in a broad range of contexts,” ACLU attorney Esha Bhandari said.

Public opinion has been divided on whether Apple should help the FBI open the phone. The latest NBC News/Wall Street Journal poll found 47 percent saying Apple should not, with 42 percent saying it should.