Customizing Pages <li> code

I would like to customize the code of the list items of the Pages widget. I want to change the class=”” to something static, and I want to add an id=”” with the dynamic stuff.

In others words change

<li class="page_item page-item-7">
<a href="http://ex.org/wp/ex" title="Example">Example</a>
</li>

to something like this

<li class="page_item" id="page-item-7">
<a href="http://ex.org/wp/ex" title="Example">Example</a>
</li>