Using <xsp:expr> into an attribute

Hi to all.
I've this XML document (home.xml)

<?xml version="1.0"?>
<?cocoon-disable-caching ?>
<?cocoon-process type="xsp"?>
<?cocoon-process type="xslt"?>
<?xml-stylesheet href="templates/home.xsl" type="text/xsl"?>
<xsp:page language="java"
          xmlns:xsp="http://www.apache.org/1999/XSP/Core"
          xmlns:xsl="http://www.w3.org/1999/XSL/Transform">
.
.
.

<xsp:content>
 <news>
  <xsl:attribute name="day">
   <xsp:expr>dateFormatter.format(todayLog)</xsp:expr>
  </xsl:attribute>
 </news>
</xsp:content>

But the generated XML document contanins explicitly
  <xsl:attribute name="day">
   <xsp:expr>2001-11-26</xsp:expr>
  </xsl:attribute>

<xsp:content>
 <news day="<xsp:expr>dateFormatter.format(todayLog)</xsp:expr>"/>
</xsp:content>

but this give me an error because I can't use "<" into the day attribute.
Any solution?