Deploy war with client certificate

With the org.codehaus.mojo tomcat-maven-plugin, it's possible to set MVN_OPTS with javax.net.ssl.keyStore, javax.net.ssl.keyStorePassword and javax.net.ssl.keyStoreType to deploy with client side SSL authentication.

I've tried setting these system properties directly in the tomcat6-maven-plugin configuration as described in https://tomcat.apache.org/maven-plugin-2.1/tomcat6-maven-plugin/examples/add-system-properties.html but somehow, these system properties are not taken into account for deploying.