Walk to Jog to Run

Seems simple enough. I have one single animation that is about 30 frames long. frames 1-10 my character is walking. Frames 11-20 he is at a slow jog, and at frames 21-30 is his full on running animation. It's a seamless transition from walking to running (splitting the animation up into parts would be no problem btw).

What I would like to do is to play this animation in Unity and have his speed increase as the animation progresses. How should I best do this? Another problem is that I need to have the final running animation loop itself over and over as well, or it would look kind of funny.

Just not sure how to start coding this.