How to manipulate image with jQuery - horizontal only

How to manipulate image with jQuery - horizontal only

I want to manipulate the image on mouseover , that only width changes ,
but the height remains same. I see the image canvas doesn't fit the actual
image, so I don't see his hand anymore. How can I just stretch the width?
http://jsfiddle.net/Z8knE/3/
div
{
background-image: url(
http://t2.gstatic.com/images?q=tbn:ANd9GcQmloy1dlrNWhp8Y2u3lEKYEnLvJAqWVhggUIrA_QwRxjenmus-Ww);
-webkit-background-size: 100%;
-moz-background-size: 100%;
-o-background-size: 100%;
background-size: 100%;
height:150px;
width:150px;
}