(CNN) He's already called for a boycott of Russia's elections in March. Now opposition activist Alexey Navalny is asking his supporters to "agitate with all our might" during nationwide protests next month.

Navalny this week was barred from challenging incumbent Vladimir Putin for the country's presidency because of an embezzlement conviction that he and his supporters contend is politically motivated.

In addition to blasting the Central Election Commission's decision to reject his registration, Navalny said the body's approval of other opposition candidates amounts to little more than a rubber stamp from Putin.

"The procedure in which we are invited to participate is not an election," he said earlier this week. "It involves only Putin and those candidates whom he personally chose, who do not pose a slightest threat to him."

US State Department spokesman Noel Clay told Russian state-run media that the United States was concerned by the CEC's decision to keep Navalny off the ballot, prompting Russia's Foreign Ministry spokeswoman Maria Zakharova to issue a statement saying the Americans were meddling in Russian affairs

"This statement by the Department of State, which will surely not be the only one, is a direct interference both in the election process and in the internal affairs of our state," she wrote.

The US State Department has previously labeled charges against Navalny as examples of "political violence" in Russia, alleging they were pursued only as a result of Navalny's activism.

''We want competitive elections'

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In a fiery blog post Wednesday, Navalny continued his attack on Putin and the CEC, calling for voters across the country to protest January 28 in support of the March 18 election boycott he is championing.

"We do not want to wait another six years. We want competitive elections right now," he wrote. "Going to the polls now is to solve Putin's problems -- help him turn reassignment into a kind of election. There is not the slightest point in this."

The exception, he said, would be voters looking to cast a ballot for the liberal Russian United Democratic, or Yabloko, Party, founded by economist and free-market advocate Grigory Yavlinsky, who has unsuccessfully run twice for the country's presidency. The Yabloko Party needs 3% of the vote to get state financing, according to Navalny, so "if you are interested to assist in this, go ahead and vote."

Navalny called on other voters to stay away from polling stations, to protest next month and to "organize an observation to prevent them from fabricating a turnout."

His campaign is already filing applications for marches and rallies "so that not one of the officials would say to us afterwards, 'Oh, the square is occupied with a belly dance competition,'" Navalny wrote.

During Navalny's pre-campaign tour, the activist's supporters arrived to find other events being held at his rally sites, including a belly-dancing competition in Samara. Navalny later complained on his blog that the belly dance music drowned out his event.

Putin: Balance impossible without competition

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The election commission rejected Navalny's registration the day after he submitted it and held nomination gatherings to kick off his campaign, according to state-run media outlet RIA-Novosti.

"A citizen who has been sentenced to imprisonment for committing a grave or especially grave crime, and who has an outstanding conviction for the said crime, has no right to be elected president of the Russian Federation," said CEC member Boris Ebzeev.

The decision was not a surprise. Navalny's candidacy was unlikely because Russian law prevents convicted criminals from running for public office. Navalny will appeal the commission's decision, campaign press secretary Ruslan Shaveddinov said Monday.

Putin, who has served as either Russia's prime minister or president since 1999, announced his intention to seek re-election -- his fourth presidential bid -- as an independent candidate during his annual press conference this month.

He said his aim was for Russia to have a "competitive" and "balanced" political system, but that it isn't his responsibility to create political opponents.

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"I want this," Putin said, "and I will strive for a balanced political system, and that is impossible without competition in the political field."

But Putin also said that most of the current opposition figures were more focused on "making noise" than on a genuine agenda that could benefit the country.

Navalny first rose to prominence during 2011's large-scale anti-government protests. He is popular among young people and has tapped into anger over a sluggish economy and endemic corruption, which could be a factor in the election.