Android :: How To Add Padding To Gradient <shape> In Phone

I have a shape with a gradient that I'm using as a divider between ListView items. I've defined it as follows:

<?xml version="1.0" encoding="UTF-8"?>
<shape
xmlns:android="http://schemas.android.com/apk/res/android"
android:shape="rectangle">

<gradient
android:startColor="#ccd0d3"
android:centerColor="#b6babd"
android:endColor="#ccd0d3"
android:height="1px"
android:angle="0" />

</shape>
I would like to add 6 pixels of padding on either side of the gradient, so that it doesn't extend from edge to edge of the screen.

However, no matter where I put an android:left="6px" and android:right="6px", it doesn't seem to take effect. I can put it in the <shape> element, the <gradient> element, or in a separate <padding> child of <shape>, and it doesn't change anything.

How can I add padding on the left and right of my list divider?