FILE - This Tuesday, July 16, 2013, file photo, shows a sign at Facebook's headquarters in Menlo Park, Calif. Facebook on Thursday, Dec. 19, 2013 said it plans to offer 70 million shares of its Class A stock in a sale that includes more than 41 million shares from chairman and CEO Mark Zuckerberg. (AP Photo/Ben Margot, File) (Ben Margot/AP)

Facebook said Thursday that it is selling an additional 70 million shares of stock, including some owned by co-founder Mark Zuckerberg, raising about $4 billion for the social media site.

The company plans to use the money for “working capital and other general corporate purposes,” it said in a Securities and Exchange Commission filing.

As part of the deal, Zuckerberg will sell 41.4 million of his class A common stock — raising more than $2 billion.

The rest of the offering includes new stock being issued by the company and some being sold by longtime Facebook investors, including Silicon Valley investor Marc Andreessen.

Zuckerberg will also exercise an option to buy 60 million shares of class B common stock, which hold more voting rights than class A common stock. Facebook expects Zuckerberg to use the profit from the sale of his A-class shares to offset his taxes related to his purchase of the B-class shares.

The transactions will slightly reduce Zuckerberg’s voting power at Facebook — down to 62.8 percent from 65.2 percent — although the executive will retain control over the company he helped launch in 2004.

Facebook is set to join the Standard & Poor’s 500-stock index, and that provided a good opportunity for it to sell more stock, company spokeswoman Vanessa Chan said.

Separately, Zuckerberg plans to buy 18 million shares of class B common stock to donate to charity this month, according to the SEC filing. A company spokeswoman confirmed that the money, about $1 billion, would go to Silicon Valley Community Foundation. Zuckerberg has donated to the California philanthropy research and investment group in the past.

Facebook has been aggressively expanding its social network since the company went public in 2012. Although it had a rocky first year on the stock market, the company’s focus on improving its presence on mobile devices and its advertising products has helped lift the stock well above its initial price of $38 per share.

The shares have surged in the past six months, nearly doubling to about $54 a share.

But Facebook is facing increasing pressure from a crop of new social networks and private­messaging companies that are attracting its key youth audience.

The company has reported that teens are spending less time on its site and that they are signing up at a slower rate. Teen users, analysts say, are instead turning to smaller services such as Snapchat, which reportedly turned down a $3 billion acquisition offer from Facebook.

To continue growing and to keep up engagement, Facebook might have to offer more products that compete with these smaller companies, either by buying them or devoting resources in-house to develop them, analysts have said. The company is already testing video advertising on its site.