R&B singer Chaka Khan has been forced to axe a series of concert dates after her doctor ordered extensive vocal rest.

The I'm Every Woman hitmaker has pulled out of four performances this month (Jun13), including an appearance at the Capital Jazz Festival in Columbia, Maryland on Saturday (08Jun13) and the Pittsburgh International Jazz Festival in Pennsylvania the following day (09Jun13).

The singer has also pushed back the July (13) release of her forthcoming album, The iKhan Project Alive, to the autumn (13) to allow her voice to recover adequately.

Her manager, Tammy MCCrary, says in a statement, "Due to her doctor's orders, it's best that we move the date (of the album release) to give her the proper and adequate time to promote and market the new album. We are looking forward to a great project and a very robust concert and tour schedule this fall."

However, Khan will attend a ceremony marking her induction into the Apollo Theater Hall of Fame in Harlem, New York on Monday (10Jun13) during the venue's 8th Annual Spring Gala Benefit.