SAN FRANCISCO - Facebook CEO Mark Zuckerberg has no intention to sell his stock for at least 12 months, said the social network company in a regular public file Tuesday.

According to a memo with the US Securities and Exchange Commission, Zuckerberg will make none of his 504 million shares reach the market for at least 12 months, and he would have to inform SEC in advance if he wants to release any of his stake.

Zuckerberg's Facebook shares currently are worth about $8.9 billion.

Meanwhile, Facebook extended the lockup expiration date, after which some employees will be able to sell their shares, to Oct 29 from Nov 14, when more than 1 billion shares will be free to enter the market.

Some Facebook insiders, including co-founder Dustin Moskovitz and early investor Peter Thiel, have begun to sell their shares in the company.

Facebook closed at $17.73 on Tuesday while it priced its IPO at $38 per share in May.