OMAHA, Neb. — Warren Buffett has decided to increase significantly the amount of stock he gives the foundations run by his three children, so they will each eventually get roughly $2.1 billion.

Buffett announced the change in his charitable giving plan on his 82nd birthday Thursday in a letter, first reported by the Omaha World-Herald.

In 2006, Buffett promised to give roughly $1.5 billion of Berkshire Hathaway stock to each of the foundations his children run as part of a plan give the bulk of his fortune to charity.

The biggest share of Buffett’s $44.7 billion fortune will go to the Bill & Melinda Gates Foundation, and another sizeable gift will go to the Susan Thompson Buffett foundation Buffett created with his first wife. He did not change those pledges.

Buffett has been giving each of the five foundations 5 percent of his total pledge annually since 2006.

Buffett said he decided to increase the amount his children will receive because of the progress they’ve made.

“I’m very pleased about how all three of them have handled the contributions in the last six years,” Buffett told The Associated Press.

Buffett said he is feeling fine and this decision was not prompted by any concern about his health. Buffett has been undergoing radiation treatment for prostate cancer this summer, but he has said his doctors do not believe the disease is life-threatening.

Each of Buffett’s three children— Howard, Susie and Peter — all chose a different focus for their foundations, based on their own interests.

Howard Buffett is helping farmers in impoverished nations produce more to help end world hunger; Susie Buffett is strengthening early childhood education and looking for ways to reduce teen pregnancy; Peter Buffett wants to empower women and girls worldwide through education, collaboration and economic development to end violence against women.

“They’ve done everything I’ve hoped for and more with the original gifts,” Buffett said.

As part of his giving plan, Buffett has always said that all of his Berkshire stock — which today includes 350,000 Class A shares and 3,770,934 Class B shares — will eventually go to charity.

The pledges to the five foundations that Buffett outlined in 2006 accounted for about 85 percent of his stock. Buffett said that increasing the amount each of his three children will receive now means that about 90 percent of his stock is spoken for.

Buffett has also been making smaller gifts of Berkshire stock to mostly unnamed charitable foundations. He said those would continue.

“As the years go by, I will commit more and more to get to that 100 percent,” Buffett said.

In his will, Buffett has specified that any shares he hasn’t already given to charity at the time of his death will go to his Susan Thompson Buffett Foundation. And he has requested that all proceeds from his giving be spent within 10 years after his estate is closed.