Former US president Carter (90) suffering from cancer
Jimmy Carter, the former American president, announced that he was suffering from cancer that had spread through his body.
The energetic 90-year-old had surgery earlier this month to remove a small mass from his liver.
In a statement, Mr Carter said he was receiving treatment in Atlanta.
"Recent liver surgery revealed that I have cancer that now is in other parts of my body," he said. "I will be rearranging my schedule as necessary so I can undergo treatment by physicians at Emory Healthcare.
"A more complete public statement will be made when facts are known, possibly next week."
The White House said President Barack Obama telephoned Mr Carter to send his best wishes for a speedy recovery.
"Jimmy, you're as resilient as they come, and along with the rest of America, we are rooting for you," he said.
Mr Carter served as president from 1977 to 1981, and has been active in causes relating to global health and diplomacy since leaving office. He was awarded the Nobel Peace Prize in 2002.
In typical fashion, Mr Carter was on an overseas mission to South America when he complained of feeling unwell in May. He was in Guyana in his role as head of the Carter Centre, monitoring national elections.
His post-president career, flying around the globe as a figure of international diplomacy, has frequently been cited as an example to other former residents of the White House.
He has lead efforts to broker peace deals in far-flung wars - from Darfur to Afghanistan - and raised awareness of human rights abuses around the world.
His group has also won credit for its 30-year role in reducing the number of cases of Guinea worm disease around the world, from more than 3.5 million to 126.
Mr Carter is the one of four living former US presidents. The others are George HW Bush, who is 91, Bill Clinton (68) and George W Bush (69).
Carter was the nation's 39th president, defeating Gerald Ford in 1976 with a pledge to always be honest.
Before his career in politics, Carter graduated from the US Naval Academy and served seven years in the Navy submarine force.
A Georgia peanut farmer who had been a state senator and governor of Georgia for a single term before running for president, Carter ended up seeing his second term for president doomed by a number of foreign policy conflicts, most especially the Iran hostage crisis - losing in a landslide to Ronald Reagan in 1980.
He spent the decades since carving out a reputation for promoting such global issues as health care and democracy, often with his wife Rosalynn by his side. He joined the staff of Emory University and in 1982 established the Carter Center to promote those issues.
His new role as global statesman took him into places often shunned by other diplomats. Carter helped defuse nuclear tensions between the Koreas and monitored the first Palestinian elections. In 2002, he won the Nobel Peace Prize.
According to the Carter Center, he and Rosalynn volunteer one week a year for Habitat Humanity, a nonprofit that helps build and renovate homes for people in need.
Despite remaining active through the years, Carter's health has recently become the subject of speculation. In May, he was forced to cut short an election observation visit to Guyana when he developed a bad cold.