Changing 2 Mono Tracks back to 1 Stereo Track on timeline, or source monitor?

I was working in Premiere Pro CS 5.5 and I switched Audio on a clip to 2 Mono Tracks instead of its original 1 stereo track. I brought it in the Source Monitor and then on the timeline.

I then realized later on that I wanted to switch the audio back to 1 Stereo Track instead of the 2 Mono tracks.

I could not figure out a way to do this.

Is it possile to do this? If so. how?

Thanks in advance?