Adding system property in testng XML?

We are trying to add a system property directly in the testng xml file, as we want to automatically run different test suites in a Jenkins job, without having different xml files for each test set. Is there a way to pass a system property directly to the file and parse it?

For example, we currently have:

<test name="Regression">
        <groups>
            <run>
                <include name="Test" />
            </run>
        </groups>

and would like to be able to have:

<test name="Regression">
    <groups>
        <run>
            <include name=$TestParameter />
        </run>
    </groups>

Thanks a lot!