Trying to mark radio inputs as selected with XSLT 1.0 using the below xslt code but this does not produced the desired result

desrired result

<input type="radio" value="available" title="email" selected="selected" />

Actual output

  <input type="radio" value="available" title="email" selected />

Anyone any ideas why not please?

XSLT

<xsl:variable name="selected">selected</xsl:variable>
  <xsl:for-each select="item">
   <tr>

     <td><xsl:value-of select="title" /></td>

     <td>
       <input type="radio" value="available" >
       <xsl:attribute name="name">
        <xsl:value-of select="title" />
       </xsl:attribute>
       <xsl:if test="category='available'">
         <xsl:attribute name="selected">
          <xsl:value-of select="$selected"/>
         </xsl:attribute>
       </xsl:if>
       </input>
     </td>

     <td>
       <input type="radio" value="unavailable" >
       <xsl:attribute name="name">
        <xsl:value-of select="title" />
       </xsl:attribute>
       <xsl:if test="category='unavailable'">
        <xsl:attribute name="selected">
         <xsl:value-of select="$selected"/>
        </xsl:attribute>
       </xsl:if>
       </input>
     </td>


     <td>
       <input type="radio" value="warning" >

       <xsl:if test="category='warning'">
        <xsl:attribute name="selected">
            <xsl:value-of select="$selected"/>
           </xsl:attribute>
           <xsl:attribute name="name">
        <xsl:value-of select="title" />
       </xsl:attribute>
       </xsl:if>
       </input>
     </td>

   </tr>

   </xsl:for-each>