How to center a SVG pattern?

How to use background-position: center; behavior on svg pattern shown below.

This is an external SVG-image, and i want to use it in <img>-tag.

<svg width="100%" height="600">
  <pattern id="pattern-checkers" x="0" y="0" width="100" height="100" patternUnits="userSpaceOnUse" >
    <rect class="checker" x="0" width="50" height="50" y="0"/>
    <rect class="checker" x="50" width="50" height="50" y="50"/>
  </pattern>
  <rect x="0" y="0" width="100%" height="100%" fill="url(#pattern-checkers)" />
</svg>