Art Garfunkel, left, with Paul Simon in 2009, is still recovering from a condition that weakens vocal cords.Art Garfunkel, left, with Paul Simon in 2009, is still recovering from a condition that weakens vocal cords. (Henny Ray Abrams/Canadian Press)

Folk-rock duo Paul Simon and Art Garfunkel have "indefinitely" postponed a North American tour that had already been rescheduled once.

They decided to put the tour on hold as Garfunkel continues to recover from a vocal paresis — which weakens vocal cords.

"This condition inhibits the duo from performing shows at the highest possible level," said a notice posted on their website Thursday.

"I do feel bad about disrupting so many people's plans but, as I continue to mend, I can't yet bring my A-game to a tour, and I would not perform for you with anything less," said Garfunkel in a statement.

Sixteen concerts in Canada and the U.S. originally set for April had been rescheduled for July, including a performance at Calgary's Pengrowth Saddledome on July 5.

Doctors said Garfunkel is expected to make a full recovery but a timeline for his recuperation is unknown.

Concert promoters Live Nation had said refunds were available.

Simon and Garfunkel, who reunited after a second breakup in 1969, were also slated to play Vancouver, Edmonton, Saskatoon, Winnipeg, Toronto, Ottawa, Montreal and Halifax.