Dolly Parton sobbed when she heard I Will Always Love You at Whitney Houston's funeral.

The 66-year-old country music legend deeply treasures the tune.

Late singer Whitney's rendition of the ballad for her 1992 movie The Bodyguard that Dolly originally penned in 1974 became an international pop sensation.

Dolly couldn't suppress her emotion when the song played at Whitney's funeral in February.

"That song will always be precious to me for many reasons. Whitney's passing made it far more emotional that it ever would be otherwise," Dolly told Fox News.

"The fact that they used it at her funeral just killed me. That's when I really lost it."

Dolly didn't ever process the full power of that song or the impact of Whitney's death until it played at that moment.

"I was shocked and hurt and disheartened when she passed, but it was one of those things where I hadn't really fell down and wept over it," she explained.

"But when they lifted her coffin and started playing that song, man it just stabbed me in the heart. I just boo-hoo'd for every singIe reason -- her loss, the fact that it was our song, and I was also thinking that was probably what they'd be playing at my funeral too! It was such an overwhelming emotion."

Dolly feels a deep connection to Whitney through their shared song.

"I will always think of this song as mine and Whitney's song because I had a number one record on it myself, and had a duet with Vince Gill on the song, but it was Whitney who took it worldwide," Dolly said. "So I'll always be very proud of that, and grateful."

Whitney passed away in a Los Angeles hotel room in February aged 48.

It was found that she accidentally drowned in the bath tub, although it was also ruled that sustained cocaine use played a part in her death.