Can I add Microdata from HTML5 to a XHTML Strict site and still be compliant?

I've got a site coded in XHTML 1.0 Strict. I want to use the new Microdata to add breadcrumbs to my site (so Google will understand them).

My old non-microdata marked-up breadcrumbs look like this:

<ul>
  <li><a href="...">Level 1</a></li>
  <li><a href="...">Level 2</a></li>
  <li><a href="...">Level 3</a></li>
</ul>

According to Google, to markup breadcrumbs using Microdata, you extend the above code like this:

<ul>
  <li itemscope itemtype="http://data-vocabulary.org/Breadcrumb">
    <a href="..." itemprop="url">
      <span itemprop="title">Level 1</span>
    </a>
  </li>
  ...
</ul>

But this is not valid XHTML 1.0 Strict.

What should I do?
Should I ignore the validation conflicts?
Should I write itemscope="itemscope" instead of just itemscope (this would be valid XML, but still not valid XHTML)?
Should I change the Doctype to be HTML5 instead of XHTML 1.0 Strict?

I want this to work all the way back to IE6!

Please advice :)