The U.S. Senate is asking questions about Apple's new facial recognition feature on the iPhone X

Apple's new iPhone X doesn't have a fingerprint sensor. Instead it uses a new kind of facial recognition technology Apple calls Face ID to unlock the phone. 

Now, U.S. Senator Al Franken wants some additional answers about how Face ID works. The Minnesota Democrat is primarily concerned about the privacy implications of Apple's new feature. 

"While I am encouraged by the steps that Apple states it has taken to implement the system responsibly, the addition of this new technology to the iPhone has serious privacy implications," Franken wrote in a Facebook post on Wednesday. 

"In a letter, I asked CEO Tim Cook a series of important questions about the iPhone X's Face ID system, including how users' "faceprints" will be protected and safeguarded, if at any point that data will be shared or sold to marketers, and whether or not law enforcement will be able to access the Face ID database," he continued. 

The letter signed by Franken lists 10 questions that he wants Apple to respond to by October 13, which is several weeks before Apple will release the iPhone X to the public. 

Questions include whether it's possible for Apple to obtain faceprint data from an iPhone X, how it trained its machine learning algorithms, and whether the Face ID systems may have racial bias. 

An Apple spokesperson did not respond to a request for comment, but some of Franken's questions have been addressed in Apple's announcement and in subsequent product briefings. However, until there's an independent technical analysis of Apple's software, many of Franken's questions remain up in the air. 

In 2016, Apple famously faced off with the FBI and then-director James Comey over an iPhone used in a terrorist attack in San Bernardino. 

The FBI wanted Apple to use its special technical expertise to help it break security on the encrypted device. Cook wrote a letter on Apple's website explaining why he was fighting that request in court. Franken asked how Apple would respond to law enforcement requests for its faceprint data on Wednesday, in a clear echo of that battle.

Franken is the ranking member of the Senate subcommittee on privacy, technology, and the law. He's sent similar letters with privacy questions to companies such as Uber, "Pokémon Go"-parent Niantic,  and even Apple in the past. 

Read the entire letter here:

Here's Franken's Facebook post: