Reese Witherspoon has revealed that she and her co-star in the new Johnny Cash biopic, Joaquin Phoenix did not hit it off right away�mainly because Phoenix could not stand Witherspoon�s voice.

The couple fell out after taking singing lessons together before filming began on �Walk The Line� and it took them months before they became friends.

Witherspoon said of the feud: "It took us about three months to trust each other because we didn't know each other at all in the beginning and we couldn't even look at each other when we had to sing to each other because it was so embarrassing.

"I'd sing too loud and he'd say, 'It's driving me crazy, she's singing too loud. Does she have to sing so loud?' I said, 'I'm just trying here!'

"It took about three months before we responded to each other's work and saw improvement. It took a long time before we really felt comfortable with each other."

"There were days we felt bad. He would say, 'You're doing really good today,' or, on days he felt like crap, I said, 'Don't beat yourself up, you're doing a really good job.'

"We really leaned on each other and became close in that way."

�Walk The Line� is released early next year.