SAN FRANCISCO, Aug. 18 - Google said in a surprise move on Thursday that it would raise a $4 billion war chest with a new stock offering. The announcement stirred widespread speculation in Silicon Valley that Google, the premier online search site, would move aggressively into businesses well beyond Web searching and search-based advertising.

Google, which raised $1.67 billion in its initial public offering last August, expects to collect $4.04 billion by selling 14,159,265 million Class A shares, based on Wednesday's closing price of $285.10. In Google's whimsical fashion, the number of shares offered is the same as the first eight digits after the decimal point in pi, the ratio of the circumference of a circle to its diameter, which starts with 3.14159265.

The company, which had nearly $3 billion in cash as of the end of June, said little about how it would spend the proceeds from the new sale, and it did not say how it would conduct the sale.

Google's filing with the Securities and Exchange Commission stated only that "we may use proceeds of this offering for acquisitions of complementary businesses, technologies or other assets."