The allegations come as part of a submission to the Copyright Office as part of its ongoing review of the Digital Millennium Copyright Act (DMCA), a piece of legislation that forbids the circumvention of copyright control mechanisms.
Apple claims that modification of the phone's software - a process known in iPhone circles as jailbreaking - could lead to major network disruptions, possibly even downing of cell sites.
As well as allowing the handset to be used on any network, the process of jailbreaking also permits iPhone users to install any software they choose, rather than Apple-permitted ones, Infosecurity notes.
Apple's arguments, filed late last month, seek to rebut a request to the agency by the Electronic Frontier Foundation that modifications to the iPhone's software do not violate the DMCA and should therefore be allowed.
The vendor's filing describes potentially severe technical problems operators could face with jailbroken phones.
Since the firmware is accessible on a jailbroken phone, Apple argues that it could be possible to reprogram a handset to gain access to the phone's baseband processor, which controls the connection to the cellular network.
"Because jailbreaking makes hacking of the BPP software much easier, jailbreaking affords an avenue for hackers to accomplish a number of undesirable things on the network," said the filing.
Apple also claims that, if several iPhones were modified to have the same serial number, it could cause a transmission tower to malfunction or kick phones off the network.
In addition, it alleges, carrier limits on data transmission could be bypassed, allowing a hacker to conduct a denial-of-service attack and so crash the cell site.
The US Copyright Office is expected to make a decision on the case later this year.