The Giving Pledge received a boost last week with ten more American billionaire families signing up to give away the majority of their wealth.

The announcement brings to 69 the number of families and individuals of exceptional wealth who have pledged to give a vast part of their fortune away in philanthropy.

The Giving Pledge was launched last year by philanthropists Bill and Melinda Gates and Warren Buffett, and targets American billionaires to publicly – although not legally – commit to distributing their wealth to charitable purposes either during or after their lifetimes.

Buffett praised the ten new pledgers and said the Giving Pledge has been gaining momentum. “We are seeing great progress in less than a year. I am delighted that so many wealthy Americans are taking a public pledge that supports philanthropy.”

Among the ten new sign-ups are co-founder of Sun Microsystems Neeru Khosla and partner, Philip and Patricia Frost, and Joyce and Bill Cummings.

The Giving Pledge remains focused on the US ultra-rich, although Gates and Buffet have held events in India and China to discuss high-end philanthropy in those countries.