Former U.S. President Jimmy Carter underwent surgery on Monday "to remove a small mass in his liver," according to his office.

The operation took place at the Emory University Hospital in Atlanta without any issues and Carter is expected to make a full recovery, according to a statement released by The Carter Center.

The country's 39th President, who will turn 91 years old in October, found the center in Atlanta after leaving the White House in 1982 to promote health care, democracy and other global issues. He completed a book tour on Saturday promoting his memoir, "A Full Life: Reflections at 90," said publisher Simon & Schuster's Julia Presser, The New York Times reported.

In May, Carter cut short a trip to Guyana, where he traveled to observe national elections, because he was feeling under the weather and returned to Atlanta. At the time, The Carter Center stated that the former President departed after "not feeling well," according to The Huffington Post.