expression syntax

I am trying to compare two dates, one in the xml data against an external
parameter holding today's date.

The format of each is yyyy-mm-dd

<xsl:for-each select="performance[date = $today]">

successfully processes records with today's date.  However, I want to select
all records equal to or later than today, but

<xsl:for-each select="performance[date &gt;= $today]">  does not select any
records.

Is my syntax wrong?

I'm using IE6 to process the files.

Thanks,
Alan