By Yasmeen Abutaleb

SAN FRANCISCO (Reuters) -- Facebook Inc Chief Executive Officer Mark Zuckerberg said on Friday he will take two months of paternity leave after his daughter's birth, though he did not say when she is due.

The 31-year-old, one of Silicon Valley's most visible leaders, did not say who would be running the company while he is out. Facebook did not immediately respond to an inquiry.

Facebook, the world's biggest online social network, allows its U.S. employees to take up to four months of paid maternity or paternity leave, which they can use all at once or throughout the first year of their child's life, which is generous by U.S. standards. Zuckerberg announced in July that he and his wife, Priscilla Chan, were expecting a baby girl.

A 2015 study by the Society for Human Resource Management found that 21 percent of employers it surveyed offered paid maternity leave, and 17 percent provided paid paternity leave. But several technology companies have recently extended parental leave allowances in an attempt to recruit and retain talent.

"This is a very personal decision," Zuckerberg wrote on his Facebook page, along with a picture of a stroller, a yellow baby carrier and his dog, Beast. "Studies show that when working parents take time to be with their newborns, outcomes are better for the children and families."

While it's unclear who will run the company in Zuckerberg's absence, it is likely that chief operating officer Sheryl Sandberg, who oversees all of Facebook's advertising, will assume leadership. Zuckerberg largely oversees products, but will likely rely on chief product officer Chris Cox while he is out.

Zuckerberg's decision is still unusual among high-level tech executives and is sure to send a message about parental leave policies and work-life balance. Yahoo Inc CEO Marissa Mayer only took two weeks off for after her first child in 2012, and when she announced she was pregnant with identical twin girls in September, she said she would be taking limited maternity leave and "working throughout."

Zuckerberg's post generated more than 50,000 'likes' in one hour and nearly 3,000 comments. Many of the comments lauded his decision and said it sent a positive message about U.S. parental leave policies.

Sheryl Sandberg, Facebook's chief operating officer, commented and congratulated Zuckerberg and his wife, Priscilla Chan. "I can't wait to meet her," she wrote.

(Reporting By Yasmeen Abutaleb; Editing by Chris Reese, Bill Rigby and Diane Craft)