Verizon Communications Inc supports "the availability of strong encryption with no backdoors," Chief Executive Lowell McAdam said on Wednesday, weighing in the showdown between Apple Inc and U.S. authorities over mobile device encryption.

"The case with Apple presents unique issues that should be addressed by Congress, not on an ad hoc basis," McAdam told Reuters in a statement.

A federal judge last week ordered Apple to create new software and take other steps to retrieve data from the locked iPhone used by Syed Rizwan Farook, one of the San Bernardino shooters who was killed in a gun battle with police.

Apple, which opposes the order, has urged the creation of a government panel on encryption.

Verizon and other telecom firms benefit from sales of Apple's iPhone and tablets. AT&T Inc said in a statement on Wednesday that there needs to be more "legal clarity" on privacy and security issues, adding that Congress should decide on safeguards.

The Justice Department has pushed back on framing the dispute as an encryption issue, insisting that it is only trying to get past the locked screen on one phone.

Many technology security experts have said technical efforts to provide government access to encrypted devices, a so-called "backdoor," inevitably degrades security for everyone. It is an argument that has been made since the 1990s, when the government tried and failed to force tech companies to incorporate a special chip into their products for surveillance purposes.

Apple has argued that while it is technically possible to bypass the security features of the iPhone by building a new operating system, such a move would set a dangerous precedent.

(Reporting by Malathi Nayak; Editing by Jonathan Oatis and Tom Brown)