Apple disputed Attorney General William Barr's assessment that it has failed to provide law enforcement with "substantive assistance" in unlocking the password-protected iPhones used by the shooting suspect at a Navy base in Pensacola, Florida, last month, but still refused his main request to provide a backdoor.

"We reject the characterization that Apple has not provided substantive assistance in the Pensacola investigation. Our responses to their many requests since the attack have been timely, thorough and are ongoing," Apple said in a statement late Monday.

Apple said it "produced a wide variety of information associated with the investigation" after the FBI's initial request on Dec. 6. The company said it provided "gigabytes of information" including "iCloud backups, account information and transactional data for multiple accounts" in response to further requests that month.

Saudi Air Force 2nd Lt. Mohammed Saeed Alshamrani shot to death three Americans at Pensacola Naval Air Station on Dec. 6. The 21-year-old gunman was fatally shot by a deputy sheriff during the attack, which U.S. officials called an act of terrorism.

Apple continues to refuse Barr's request that it help find a way for law enforcement to access encrypted devices with a court order, like the one Apple resisted in 2016 in the case of a shooter's iPhone in San Bernardino, California. In that case, the point was dropped when the FBI was able to crack into the phone without Apple's help, but the incident raised questions about the balance between civil liberties and public safety that have yet to be settled.

"We have always maintained there is no such thing as a backdoor just for the good guys," Apple said in its latest statement. "Backdoors can also be exploited by those who threaten our national security and the data security of our customers. Today, law enforcement has access to more data than ever before in history, so Americans do not have to choose between weakening encryption and solving investigations. We feel strongly encryption is vital to protecting our country and our users' data."