Former US president George HW Bush said Friday shaving his head in support of a young leukemia patient whose father is in his security detail was "the right thing to do."

The former president was interviewed at the Bush family compound in Kennebunkport, Maine, by his granddaughter Jenna Bush Hager, a correspondent with NBC's Today show.

"A lot of the agents shaved their heads, and I said why not me?" Bush told his granddaughter. "It was the right thing to do."

A photo released Wednesday by Bush's office showed two-year-old Patrick, who is undergoing leukemia treatment and the elderly ex-president each sporting bald heads and similar blue polo shirts and khakis.

Members of Bush's Secret Service security detail also shaved their heads in solidarity with the young boy.

Bush said that he simply wanted to "bring happiness" and "just identify" with Patrick.

The former president's wife, Barbara Bush, said she was "surprised and thrilled" by the president's new do.

"I think he looks beautiful. He looks younger," she said.

The former first lady recalled how the couple had lost their second child, Robin, to leukemia nearly 60 years ago, just before her fourth birthday.

Bush, 89, the oldest living former US president, served in the White House from 1989 to 1993. He was honored last week at the White House by US President Barack Obama for his engagement in volunteerism and his "Points of Light" volunteer program.

Known for his love of skydiving, Bush celebrated his 75th, 80th and 85th birthdays by parachuting to earth.

The ex-president, who was seated in his wheelchair during the interview and spoke with a more feeble voice than in years past, intended to go skydiving again on his 90th birthday, Bush Hager said.