Russian President Vladimir Putin said Thursday that Moscow will retaliate if the United States takes measures against Kremlin-controlled media group RT.
Washington is pressuring the channel to register as a "foreign agent", which would force it to disclose personal information of employees and those interviewed.
Speaking at the annual Valdai Club meeting of international experts in Sochi, Putin said Moscow would take similar actions against US media in Russia if legal steps are taken to limit RT's activities in the United States.
"We will act in a way that reflects their moves and we will do this quickly. As soon as we see steps being taken that limit the actions of our media there will be a tit-for-tat response," he said.
Putin praised RT as "doing brilliant work" and said the channel was much smaller than the dominant US and British media working internationally, which he called the "Anglo-Saxon monopoly".
RT this month said the channel was given a deadline of October 17 to register under the Foreign Agents Registration Act (FARA).
The Russian justice ministry also sent warning letters to "a number of US media operating in Russia" warning them of the "unacceptability of breaching Russian law".
Russia has a law requiring non-governmental organisations with foreign funding to register as foreign agents, but it has never been used to target media organisations.
The law has instead led to the shuttering of dozens of groups working on anything from environmental protection to HIV prevention.
Relations between Moscow and Washington have plummeted to their lowest level since the Cold War and numerous investigations in the US are looking into whether Russia meddled in 2016 elections to swing the vote in favour of President Donald Trump.