Dozens of wealthy families have joined the pledge.
Buffett and Gates recently sat down with ABC's Christiane Amanpour to discuss their visions of philanthropy. Melinda Gates joined her husband for the interview.
Amanpour also spoke with media mogul Ted Turner, who has pledged his wealth away.
Bill and Warren spent some time a while in China to promote the same idea. But, it didn't work out well. They did not push mega-wealthy families to sign up for their campaign because China had to develop its own culture of philanthropy.
Philanthropy in China has complications beyond issues like possible waste or corruption that might worry Western donors. Some wealthy Chinese fear generous donations could expose fortunes larger than the government or rivals had calculated, inviting unwanted attention.