"The United States is troubled about efforts by Russian authorities to crack down on the political opposition," State Department spokeswoman Heather Nauert said.
"Confident political leaders do not fear competing voices, nor see the need to misuse legal authorities to prevent peaceful protests and detain political opponents."
The statement came after opposition politician Alexei Navalny was briefly detained on Sunday after thousands rallied against an election expected to extend Vladimir Putin's term.
And it came as Washington was expected to announce a new raft of sanctions targeting some of Russia's richest business leaders for their alleged ties to Putin's inner circle.
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"We urge the Russian government to provide a level playing field for all political parties seeking to compete in the electoral process."
The Russian opposition, including Navalny's supporters, has threatened to boycott what they see as the March "pseudo- polls," all but guaranteed to hand Putin a historic fourth term.
But Putin's spokesman Dmitry Peskov has dismissed the threat, arguing that Putin's popularity as "the absolute leader of the political Olympus" is great enough to see off any challenge.