Google (GOOG) executive chairman Eric Schmidt plans to sell a big chunk of his stake in the Web search company.

Schmidt, who was Google's CEO from 2001-2011, will sell up to 3.2 million shares of Google stock, worth about $2.5 billion, according to a filing with the SEC late Friday.

That would leave him with 4.4 million shares, or a 1.3% stake, and 5% voting power. That's a little more than half of what he owned at the end of last year.

Schmidt owned 7.6 million shares, which gave him 8.2% of the voting power, as of Dec. 31. This sale is part of a pre-arranged stock trading plan the company approved in November that allowed Schmidt to begin selling his stock this month.

"Using this trading plan, Eric can diversify his investment portfolio and can spread stock trades out over a period of one year to reduce market impact," said Google in the filing.

Just last week, Google's stock soared to an all-time high on hope that the company was nearing a settlement with European regulators over an antitrust probe. Turns out the European Commission says it's still reviewing proposals submitted by Google. But the hint of a settlement was enough for investors to jump in.

Related: 5 reasons why Google has its mojo back

Google's stock has been on a tear over the past six months as the company continues to activate a million Android devices a day, has successfully expanded into the broadband, cable and wireless arenas, and remains the dominant search engine.

Despite more competition from Microsoft (MSFT) and Facebook (FB), neither has yet threatened Google's top spot.

Shares of Google edged lower in after-hours trading.

-- CNNMoney's David Goldman contributed