Moscow (CNN) Russia's best-known opposition leader, Alexei Navalny, has accused the regime of President Vladimir Putin of being "built on corruption" and called on the Kremlin to mend battered relations with the West.

As Russia braces for a day of nationwide anti-Kremlin rallies on Sunday, Navalny, who has been barred from standing in the March 18 presidential elections, claimed Putin was scared of opposition.

In an exclusive interview with CNN at his Moscow headquarters, he warned of growing impatience for political change. "Putin has been in power for 18 years now," Navalny said. "People are not ready to wait another six years, then another six, then another."

The 41-year-old anti-corruption campaigner said his supporters will take to the streets in more than 100 towns and cities across Russia on Sunday in a rare show of political defiance.

Navalny said people blamed the regime for their plight. "The Putin regime is built on corruption," he told CNN. "According to official data, over 20% of our population lives below the poverty line. And people link the obvious. Why are we so poor? Because they steal so much," he said, referring to Russia's ruling elite.

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