Harrington, who has won three majors and played in six successive Ryder Cups from 1999 to 2010, was a vice-captain when Europe took back the cup under Thomas Bjorn at Paris's Le Golf National last year.
The Irishman, who discovered over Christmas that he had broken a bone in his wrist that will delay him starting his 2019 season until February, was on the winning team in 2002, 2004, 2006 and 2010.
The 47-year-old has been odds-on favourite to captain at Whistling Straits in Wisconsin next year. He also has experience of the course from PGA championships appearances.
England's former world number one Lee Westwood, who was one of the five European vice-captains in 2018, has indicated a preference for captaining Europe in Italy in 2022 when Rome hosts the biennial event.
(Reporting by Alan Baldwin, editing by Ed Osmond)