Kevin McCoy, and Kevin Johnson

USA TODAY

The Department of Justice said Friday it is pressing forward in its legal fight to force Apple's assistance in unlocking an iPhone linked to a drug conspiracy case in New York City.

In a one-page letter filed in a New York federal court, DOJ lawyers said the government "continues to require Apple's assistance in accessing the data'' on the iPhone of Jun Feng, a Queens, N.Y., suspect who pleaded guilty in a methamphetamine conspiracy case.

The Brooklyn federal court filing came a week after the government abruptly withdrew from a similar high-profile legal challenge in California after the FBI was able to access the contents of the iPhone used by San Bernardino terrorist Syed Farook, using a method developed by an undisclosed outside party.

The government's position signals a continuing legal battle that pits privacy issues against law enforcement and national security concerns. The issue has drawn contrasting legal arguments from tech companies, civil liberties experts and government authorities across the nation and beyond.

The smartphone in the Brooklyn federal court case is an iPhone 5S, running on Apple’s iOS7 operating system. Both the model and operating system are different from the iPhone in the San Bernardino case.

Federal investigators ran tests to determine whether the third-party method that enabled them to extract data from the San Bernardino iPhone would work on other Apple models, a senior law enforcement official said Friday. The government representative was not authorized to comment publicly on the pending legal matter and spoke on condition of anonymity.

Asked whether investigators had tested the third-party extraction method on the iPhone in the Brooklyn case, the official cited FBI Director James Comey’s statement Wednesday that the method works only on a "narrow slice" of iPhones, not all models.

"In this case, we still need Apple’s help in accessing the data, which they have done with little effort in at least 70 other cases when presented with court orders for comparable phones running iOS 7 or earlier operating systems,'' Justice spokeswoman Emily Pierce said.

Apple attorneys said Friday that the company, though disappointed with the government's decision to proceed in the Brooklyn case, would defend its position in court and attempt to force the FBI to disclose the method it used to unlock the San Bernardino phone. The company plans to seek assurance that the government exhausted all options for accessing the contents of the phone in the drug case.

The attorneys, who spoke on the condition that Apple's representatives not be publicly identified, asserted that a full vetting of the method used by the FBI in the San Bernardino investigation would be a core part of Apple's legal strategy in Brooklyn.

The company, the attorneys said, has the right to know what steps the FBI took to get access to the data on Feng’s iPhone before seeking to compel the tech giant to assist them.

Apple contended the Justice Department's decision in the Brooklyn matter underscored an intention by federal authorities to set a legal precedent that could be applied to other investigations.

Comey: Hack tool used on San Bernardino phone won't work in new models

Apple’s technical experts previously told investigators the company had the capability to extract data from the iPhone in the Brooklyn case, the law enforcement official said.

After complying with dozens of similar government requests for assistance under the federal All Writs Act, Apple filed a motion in October saying it would not comply with the request.

Brooklyn federal court Magistrate Judge James Orenstein denied the government's motion in a decision March 3 that said government lawyers had not proved the All Writs Act applied in the case.

Apple doesn’t have to unlock drug dealer’s iPhone, judge says

The legal question "is not whether the government should be able to force Apple to help it unlock a specific device; it is instead whether the All Writs Act resolves that issue and many others like it to come," Orenstein wrote. He concluded the 1789 statute was not applicable.

Justice subsequently appealed the ruling. The legal battle is before Brooklyn U.S. District Court Judge Margo Brodie. Apple is scheduled to file a response to the government’s application by April 15.

“There will be cases all the time in which information may or may not be on an iPhone, and there is no precedent here," said Mark Bartholomew, a University at Buffalo law professor in New York whose teaching and research focuses in part on cyberlaw and encryption issues.

"What I think may happen is Congress will weigh in," Bartholomew said. "Pressure and attention has kicked up, and Congress is in the best position to weigh the balance on privacy and security and maybe construct something more fine-tuned than a court-by-court basis."

Hours after Justice's filing, draft legislation was circulating on Capitol Hill that would force tech companies to hack encrypted devices in response to a court order.

The legislation from Senate Intelligence Committee Chairman Richard Burr, R-N.C., and Vice Chair Dianne Feinstein, D-Calif., would effectively derail the growing use of "end-to-end" encryption, which is designed to be so strong that only users have the ability to get into their smartphones, tablets and other electronic devices.

Contributing: Jessica Guynn and Erin Kelly