A sparkling diamond ring owned by child star turned diplomat Shirley Temple Black throughout her long, fabled life goes under the hammer in New York next month valued at $25-35 million, Sotheby's said Friday.

Temple's father bought the ring in 1940, while World War II was raging in Europe, for the then princely sum of $7,210 around the time of her 12th birthday.

The 9.54-carat deep blue diamond ring will be auctioned in New York on April 19, Sotheby's said.

The iconic child star, who delighted movie-going audiences with her singing, dancing and simple innocence during the hardship of the American Great Depression started acting at three.

In 1935, aged six, she became the youngest person to win an Oscar, and went onto star in more than 40 feature films, most of them before the age of 12.

Later in life, she served as a diplomat under four presidents, including as US delegate to the United Nations, and ambassador to Ghana and to Czechoslovakia.

She became the first female US chief of protocol at the State Department from 1976-77 under president Gerald Ford. She died in California in 2014 aged 85.