"President Carter is in very good spirits, appreciates all the good wishes being sent his way, and looks forward to getting back to his busy schedule," MetroHealth Medical Center in Cleveland, Ohio, said in a joint statement with the Carter Center.

Earlier the hospital said Carter was "feeling normal."

Carter, who turns 86 on Friday, developed an upset stomach during a flight to Cleveland where he was scheduled to attend a book signing for his new book, "White House Diary." He was taken to the hospital from the airport by ambulance.

Carter has been active in international diplomacy since serving as president from 1977 to 1981, particularly in intervening on behalf of Americans detained abroad and as an observer of foreign elections.

The Carter Center, which is based in Atlanta, works to promote peace, human rights and global health.

Carter won the Nobel Peace Prize in 2002.