"Such acts represent an egregious violation of journalistic freedom, and are particularly disheartening to witness in the country that positions itself as the global champion of free press," the broadcaster said in a statement.
RT pledged to "apply the full weight of its legal team" to provide support to its journalist, according to the press service.
"We are confident that a thorough review by the U.S. Attorney’s office will confirm that Alexander, who wore his press credentials at all times, was wrongfully arrested," the press office stressed.
Rubinstein, along with Evan Engel of Vocativ and freelance journalist Aaron Cantu, was arrested and charged with inciting to riot on January 20. The journalists were released with preliminary hearing in the cases scheduled for February. If convicted, the journalists may be sentenced to up to 10 years imprisonment and will have to pay $25,000-fines.