XML shape android

i have a shape an oval that i made rounded and i want to add a smallest oval but at the center of this one with another color i'm tring to do this but i can se the smallest and they always have the same size

Can i overlay two shape without masking the other i did this but i can see the smallest shape :

<?xml version="1.0" encoding="utf-8"?>
<layer-list xmlns:android="http://ift.tt/nIICcg">

    <item

        >
        <shape android:shape="oval">
            <size android:width="170dp"
                android:height="170dp"/>
            <solid android:color="#f00"/>
        </shape>
    </item>
    <item >
        <shape android:shape="oval"

            >
            <size android:width="140dp"
                android:height="140dp"/>
            <solid android:color="#f000"/>
        </shape>
    </item>


</layer-list>