Image copyright Getty Images Image caption Mark Zuckerberg and his wife Priscilla with their baby girl called Max

Facebook's Mark Zuckerberg and his wife Priscilla Chan say they will give away 99% of their shares in the company to good causes as they announce the birth of their daughter Max.

Mr Zuckerberg made the announcement in a letter to Max on his Facebook page.

He said they were donating their fortune to the Chan Zuckerberg Initiative to make the world a better place for Max to grow up in.

The donation amounts to $45bn (£30bn) at Facebook's current value.

However the shares will not be donated to charity immediately, but over the course of the couple's lives.

Were Mr Zuckerberg to give away 99% of his shares immediately, he would still possess hundreds of millions of dollars. Ms Chan's worth has not been documented.

Max was born last week, although her birth was only made public on Tuesday.

In his letter Mr Zuckerberg said the aim of the Chan Zuckerberg Initiative is "to advance human potential and promote equality for all children in the next generation".

Its initial areas of focus will be personalised learning, curing disease, connecting people and building strong communities.

Image copyright Reuters Image caption Both Ms Chan and Mr Zuckerberg are taking parental leave

"Your mother and I don't yet have the words to describe the hope you give us for the future," Mr Zuckerberg said at the start of his letter to Max.

"You've already given us a reason to reflect on the world we hope you live in," it added.

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Dave Lee, BBC North America Technology Reporter, San Francisco

Billionaire investor Warren Buffet congratulated Zuckerberg and Chan, proclaiming that when it comes to giving away your fortune, "30 is the new 70".

No longer should billionaires wait to die before handing over money to a different generation, Buffet said, in a gushing approval of Silicon Valley's newest and most influential power couple.

Everything Mark Zuckerberg does is eyed with intense scrutiny, not least due to the nature of Facebook's business of making money from personal data.

But while the 31-year-old's previous charitable efforts have been criticised for being too focused on building Facebook's user base, this latest pledge appears to leave the Facebook business to one side.

It's a continuation of what we've seen developing over the past six months, where Zuckerberg appears at ease hosting heads of state as he does in the company of his own development team.

The days of Mark Zuckerberg being seen as a nerdy, awkward tech dork are well behind us.

His ambition now is clearly to be a significant figure on the global political stage.

Read more: Silicon Valley's new power couple

The letter highlighted the important role of technology in achieving the couple's goals of advancing human potential and equality.

Media playback is unsupported on your device Media caption But who is the most generous philanthropist of all?

"Many of the greatest opportunities for your generation will come from giving everyone access to the internet," Mr Zuckerberg wrote to his daughter.

He said more details about the donation will be released once he and Ms Chan return from paternity and maternity leave.

Mr Zuckerberg said he will remain chief executive of Facebook for "many, many years to come".

In a filing to the US Securities and Exchange Commision, Facebook said that Mr Zuckerberg "plans to sell or gift no more than $1bn of Facebook stock each year for the next three years and that he intends to retain his majority voting position...for the foreseeable future."