An Apple store in Shanghai
An Apple store in Shanghai. Image Credit: Bloomberg

US President Donald Trump called for Apple Inc. to "step up to the plate" and suggested the company unlock iPhones used by the gunman behind the Dec. 6 terrorist attack on a Florida Navy base.

In a tweet on Tuesday, Trump said the U.S. government helps Apple on trade and other issues, so in return, the Cupertino, California-based technology giant should unlock phones used by "criminal elements."

Trump and Apple Chief Executive Officer Tim Cook have cultivated a unique working relationship, and these ties likely contributed to Trump negotiating a trade deal with China that will potentially save Apple billions of dollars.

Still, U.S. government officials, including Trump's Attorney General William Barr, have complained that Apple isn't doing enough to help unlock the iPhones of the Florida attacker.

Apple rejected the assertion that it hasn't helped, saying that it provided "gigabytes" of data from to cloud backups of the devices.

Apple didn't directly address the government's request for it to unlock the devices, but is refusing to build special tools to give investigators access to locked iPhones.

However, the government doesn't need Apple to break into and analyze the attacker's handsets and can instead use third-party tools, Bloomberg News reported earlier Tuesday, citing security experts. One tool to simplify this process was updated on Tuesday.

Trump's tweet is an escalation of a long-running public spat between Apple and the FBI over device security and data encryption.

In 2016, the FBI asked Apple to unlock an iPhone belonging to a shooter behind the San Bernardino terrorist attack. Apple refused, and CEO Cook said building a backdoor into the devices was the "software equivalent of cancer."