Set system property inside TestNG XML suite

I have a test suite like this:

<suite name="MySuite">
    <parameter name="key" value="val"/>
    <test name="testing">
        <packages>
            <package name="mypack.testpackage.*"/>
        </packages>
    </test>
</suite>

but I need to use key as a system property instead of a parameter (because I use it later in some Spring ELs where I can't use @Parameters to take its value).

So I'd like to use something like:

    <system-property name="key" value="val"/>

or

    <parameter name="key" value="val" system-property="true"/>

instead of the parameter

    <parameter name="key" value="val"/>

Does TestNG support this?