Former US President Jimmy Carter said on Wednesday that recent liver surgery revealed he had cancer that had spread to other parts of his body.

"I will be rearranging my schedule as necessary so I can undergo treatment by physicians at Emory Healthcare," Carter, 90, said in a statement. "A more complete public statement will be made when facts are known, possibly next week."

Carter, a Democrat, served as the 39th president from 1977 to 1981 after defeating Republican incumbent Gerald Ford. He was defeated for re-election in 1980 by Republican Ronald Reagan.

The Carter family has a history of pancreatic cancer, including his parents, two sisters and younger brother Billy Carter who all died from the disease.

Carter told the New York Times in 2007 that he and other relatives had given blood for genetic studies seeking to help doctors diagnose the disease.

Asked why he has escaped the disease for so long while it devastated the rest of his family he blamed smoking. "The only difference between me and my father and my siblings was that I never smoked a cigarette," said Carter, former governor of Georgia and a state senator. "My daddy smoked regularly. All of them smoked."

Carter's health became a matter of concern in recent months after he cut short a trip to Guyana in May to observe national elections. At the time, the Carter Center in Atlanta said only that he had returned to his home state of Georgia after "not feeling well".

The Carter Center said last week that he had undergone elective surgery at Atlanta's Emory University Hospital to remove a small mass in his liver and his prognosis was excellent.

Democratic President Barack Obama, who is vacationing on Martha's Vineyard, Massachusetts, spoke with Carter on Wednesday "to wish him a full and speedy recovery," White House spokesman Eric Schultz said.

"Jimmy, you're as resilient as they come, and along with the rest of America, we are rooting for you," Obama said in a statement issued by the White House.

Republican Georgia Governor Nathan Deal and his wife issued a statement saying Carter was "in their prayers as he goes through treatment".

Carter also received words of sympathy and encouragement via Twitter from former CNN host Larry King: "We go back many years. Stay strong Mr President."

A Nobel Peace Prize winner and activist on a range of issues from global democracy to women and children's rights, as well as affordable housing, Carter published his latest book last month, titled "A Full Life: Reflections at Ninety."

In July, he gave a wide-ranging interview to Reuters Editor-at-Large Sir Harold Evans on his life from his childhood on a Georgia peanut farm to his presidency. 

Carter recalled growing up in a home without running water or electricity, at a time when he said the daily wage was $1 for a man and 75 cents for a woman, and a loaf of bread cost five cents.

He said the civil rights movement led to important progress toward racial equality in the United States, but lamented "there's still a great prejudice in police forces against black people and obviously some remnants of extreme racism".