Animation move from right to left

I have this little animation in javascript, which makes my background move though, this has times that moves from right to left and has other times that moves from left to right.

How would you always move from right to left.

Code:

        $('#cores').animate({
 'background-position-x': cd.position
},{ duration: 6000, 'easing':'easeOutCubic'

Thank you.