Former US president Jimmy Carter (85) has been hospitalised in Cleveland, Ohio.
It is understood Mr Carter fell ill on a flight to the city. Mr Carter’s plane was met by paramedics on landing at Cleveland’s Hopkins International Airport.
A spokeswoman for Mr Carter said the former president "is resting comfortably" at Metro Health Hospital in Cleveland and "is expected to resume his book tour this week."
He was heading to the city for a signing session for his new book White House Diary when he fell ill.
Mr Carter served as 39th President of the United States from 1977 to 1981 and was the recipient of the 2002 Nobel Peace Prize.
Since leaving the presidency, Mr Carter has been active in international diplomacy, particularly in intervening on behalf of Americans detained abroad and as an observer of foreign elections.
Just last month, he went to North Korea to secure the release of an American who had been convicted of illegally entering the country. Carter left Pyongyang with Aijalon Mahli Gomes, who was arrested in January and sentenced to eight years of hard labour.
He made waves this month with the publication of his White House Diary and accompanying interviews in which he fiercely criticised the late Senator Edward Kennedy, a fellow Democrat, for his approach to reforming US healthcare.