Willie Nelson. Picture: AP

US singer-songwriter and country music star Willie Nelson on Thursday cancelled his current North American tour, citing a health problem.

The 86-year-old music legend made the announcement in a tweet addressed to his fans after performing in Toledo, Ohio.

"I'm sorry to cancel my tour, but I have a breathing problem that I need to have my doctor check out," Nelson said. "I'll be back."

Nelson, whose hits include "On The Road Again" and "Always on My Mind," had been touring with Alison Krauss and was next set to take the stage in Grand Rapids, Michigan, on Friday.

It was unclear whether the entire tour, which is set to run through November 29, would be cancelled as a result of Thursday's announcement.

A representative of Nelson was quoted by "Rolling Stone" as saying he would perform at Farm Aid, a festival he founded, on September 21, alongside Neil Young, John Mellencamp, Dave Matthews, and Bonnie Raitt.