The high-stakes legal fight between Apple and the US Justice Department over a locked iPhone is moving from the courts to Congress.
FBI Director James Comey and Apple chief lawyer Bruce Sewell are appearing before the House Judiciary Committee in Washington for a hearing on encryption on Tuesday.
The hearing comes amid two significant and conflicting court rulings in New York and California on whether Apple can be forced to help the FBI gain access to locked phones.
Mr Comey warns in his prepared testimony that technological advancements have been accompanied by "new dangers".
He says those can prevent law enforcement from collecting critical evidence in criminal and terrorism investigations.
But Mr Sewell says the FBI is asking Apple to weaken the security of its products, which he says could create a dangerous precedent.