Google's shares were first floated on the market a year ago

The stock sale, which comes as Google celebrates its first anniversary as a listed company, will partly be used to help fund possible acquisitions.

Google stressed that it had no current deals in the offing, and it also would use the money to fund running costs.

Shares in Google lost $5.09, or 1.79%, to close at $279.75 on Thursday.

China beckons

We believe the company is building a war chest for future acquisitions Mark Rowen, Prudential analyst

"The principal purpose of this offering is to obtain additional capital," Google said in a filing with the US Securities and Exchange Commission.

The company said that until suitable buying opportunities arose, it would invest the proceeds of the offering in "highly liquid, investment grade securities".

"We believe the company is building a war chest for future acquisitions," said Prudential analyst Mark Rowen in a note to clients.

Citigroup analyst Mark Mahaney said he expected Google to "use the proceeds for an acquisition, most likely in international markets."

Commentators have suggested that Google may use the cash to gain a stronger foothold in China, following a move by internet rival Yahoo to take a 40% stake in Chinese auction website Alibaba.com.

Merrill Lynch analyst Lauren Rich said Google could have Chinese internet search engine Baidu.com in its sights. Baidu's shares soared 350% on their first day of trading on the US Nasdaq stock exchange earlier this month.