Los Angeles, California - Dolly Parton's sister on Tuesday asked fans to pray for the country star, who has postponed several concerts due to health issues.

Parton (79) last week delayed her upcoming Las Vegas gigs due to unspecified "health challenges," and disclosed that she was set to undergo multiple medical procedures.

"Last night, I was up all night praying for my sister, Dolly. Many of you know she hasn't been feeling her best lately," wrote Freida Parton on her Facebook page.

"I truly believe in the power of prayer, and I have been lead to ask all of the world that loves her to be prayer warriors and pray with me."

Dolly Parton had been set to perform six nights of sold-out shows in December at Caesars Palace.

The Jolene and I Will Always Love You singer scrapped those dates last week because her current health meant she would not "be able to rehearse and put together the show that you want to see."

Parton told her millions of followers that she was not ending her glittering career just yet, and said new dates were set for next September.

Parton became a major star in the 1970s, with singles including Coat of Many Colors, and followed up with smash hits like I Will Always Love You, famously covered by Whitney Houston, and 9 to 5.

She is due to receive an honorary Oscar next month, but Hollywood trade publication Variety said Parton is no longer expected to attend the Los Angeles ceremony.

Her sister Freida ended her plea for prayers Tuesday with an upbeat note.

"She's strong, she's loved, and with all the prayers being lifted for her, I know in my heart she's going to be just fine," she wrote. "Godspeed, my sissy Dolly. We all love you!"