variable width button layout

I'm currently trying to make a button with a border around it. This border however needs a different width on different sides, for example 10px on left and rigt and 5px on top and bottom. I've managed to create a rectangle with a 10px border using shape. Code is below. My question is how can I decrease the border width on arbitrary sides?

<?xml version="1.0" encoding="utf-8"?>
<layer-list xmlns:android="http://ift.tt/nIICcg">
    <item>
        <shape android:shape="rectangle">
            <gradient android:startColor="#FFFFFF"
                android:endColor="#7A7A7A"
               android:angle="270" />

            <corners android:radius="3dp" />
           <stroke android:width="10px" android:color="#000000" />
        </shape>
    </item>
</layer-list>