"The law is mandatory for everyone. We will enforce the law by all means [necessary], or the company will stop operating in Russia," Roskomnadzor chief Aleksandr Zharov told reporters on September 26.
"We will insist on Facebook's...compliance with Law No. 242," he said of the data storage legislation that President Vladimir Putin signed in 2014. "That will certainly happen in 2018."
Zharov said that the Russian government understands that Facebook is a "unique service" but said it will not make exceptions and will have to block it next year if Facebook does not comply.
Roskomnadzor blocked the professional-networking website LinkedIn in November 2016, saying it failed to comply with the law.
Putin's government is seeking to reduce its reliance on foreign technology amid severe tension between Moscow and the United States.