Google Inc. co-founders Larry Page and Sergey Brin each plan to sell up to 7.2 million shares of their stock in the online search engine leader during the next 18 months -- divestitures that would generate more than $1 billion for each at current prices.

Mountain View, Calif.-based Google disclosed the intentions of Page and Brin, both 31, late Friday in documents filed with the Securities and Exchange Commission. In the same filing, Google also revealed that its chief executive, Eric E. Schmidt, plans to sell 2.2 million shares.

Google's shares gained $1.86, or 1.1 percent, to close at $169.40 Friday on the Nasdaq Stock Market. Based on that price, Page and Brin would each pocket $1.2 billion from their sales while Schmidt, 49, would collect $373 million.

The company's stock price is nearly double its $85-per-share price at its Aug. 19 initial public offering.

Page, Brin and Schmidt will retain most of their company stock. If the planned sales are completed, Page and Brin would still own about 31 million shares apiece -- stakes worth more than $5 billion as of Friday. Schmidt would still own 12.2 million shares -- currently worth more than $2 billion.

Page, Brin and Schmidt plan to sell their stock through automated trading programs -- a common tactic that corporate executives use so investors don't question the timing of their divestitures. They adopted the plans in mid-September, but Google didn't reveal the details until Friday.

Some investors fear a sharp decline in the share price if hundreds of insiders began to cash out the holdings that they have accumulated since the popular Internet search engine's debut in 1998.

The selling restrictions on 39.1 million shares held by Google insiders were lifted Tuesday, contributing to a one-day decline of nearly 7 percent.

The insider selling has already begun. In a separate SEC filing Friday, venture capital firm Kleiner Perkins Caufield & Byers disclosed that it sold 5.78 million shares Wednesday for $997 million, or $172.45 per share. The Menlo Park, Calif.-based firm had invested $12.5 million in Google in June 1999.