It marks a dramatic escalation in Reed's battle to secure his freedom, with his family expressing growing frustration with the Biden administration for not doing enough, they said.
Reed's Russian girlfriend told ABC News that he started his hunger strike last Thursday, Nov. 4. His family confirmed the news through his Russian attorney, saying in a statement Monday that he is protesting "his arbitrary detention and Russian authorities' numerous and flagrant violations of his basic human rights and his rights under Russian law."
Reed has been in solitary confinement for nearly three months now, and he has not been able to contact his family in nearly four months. The former Marine presidential guard has been in Russian custody since August 2019, sentenced to nine years last July for assaulting two police officers. The U.S. embassy in Moscow has called the trial absurd, as the two officers struggled to recall the alleged incident in court hearings and contradicted themselves repeatedly.
In a labor camp in the remote Mordovia region for months now, Reed has been confined to a small cell that doesn't include a toilet, and items that U.S. Ambassador to Russia John Sullivan brought for him when he visited in September have not been given to him by prison guards, according to his family.
"Our concern is magnified by Russian authorities' decision to hold Trevor incommunicado which makes it impossible for us or the Embassy to monitor his health," they said.
After President Joe Biden met Russian leader Vladimir Putin in June, there was hope for and speculation about a prisoner swap, especially because Biden said he raised his case and that of Paul Whelan, another U.S. citizen detained by Russia.
But there was no deal reached in the weeks and months that followed, and a family representative told ABC News that they are not aware of any talks ongoing right now to free Reed.
In their statement, the Reed family urged the Biden administration to exchange one of the two Russians whose names have been floated publicly by Russian state media and senior Russian officials as a possible exchange. Viktor Bout, known as the "Merchant of Death" because of his notorious work as a prolific arms dealer, is serving a 25-year sentence in U.S. federal prison, while Konstantin Yaroshenko is serving a 20-year sentence for attempting to smuggle cocaine and other illicit drugs to the U.S. as a pilot.
While Reed's family members note they have been "patient," it's clear they are getting increasingly frustrated and anguished. They said Monday they hope Biden and his national security adviser Jake Sullivan "will find the time to see us" when they next visit Washington and "find the political will to bring our son home."
But while they said they "look forward to our son receiving" the administration's attention for his hunger strike, the State Department was succinct on the subject. Spokesperson Ned Price said Monday that the agency is aware of reports of Reed's hunger strike, but declined to comment further, citing privacy concerns.
Ambassador Sullivan last visited Reed in prison camp on Sept. 22 and will try to visit him again this month, Price added, as well as Whelan.
ABC News's Tanya Stukalova and Patrick Reevell contributed to this report.