Democratic Rep. Barbara Lee said Friday evening that she is concerned that President Trump is placing the "executive branch in the hands of an extremist" by announcing Homeland Security Secretary John Kelly as his new chief of staff.

"By putting Gen John Kelly in charge, Pres Trump is militarizing the White House & putting our executive branch in the hands of an extremist," Lee, who hails from California, said in a tweet.

By putting Gen John Kelly in charge, Pres Trump is militarizing the White House & putting our executive branch in the hands of an extremist. — Rep. Barbara Lee (@RepBarbaraLee) July 28, 2017

Her criticism came shortly after Trump tweeted that Kelly would be taking Reince Priebus' job.

It is unclear what exactly irks Lee about Kelly. The former Marine general has taken a hardline stance on illegal immigration enforcement as head of DHS, which has seen illegal immigration sharply decline in the first six months of the Trump administration.

Kelly was confirmed as the DHS chief by the Senate by an 88-11 vote on Jan. 20. Though most Democrats supported him, some disliked his refusal to embrace former President Barack Obama's executive orders granting some of the protections of legal status on children brought to the United States illegally.

Kelly officially starts his new job on Monday.