log4j logger set default priority

Question

I have an standalone java application with following config log4j.xml:

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE log4j:configuration SYSTEM "log4j.dtd">
<log4j:configuration xmlns:log4j="http://jakarta.apache.org/log4j/">

    <appender name="file" class="org.apache.log4j.RollingFileAppender">
        <param name="maxFileSize" value="1MB" />
        <param name="maxBackupIndex" value="1" />
        <param name="File"
            value=".\\myComp.log" />
        <layout class="org.apache.log4j.PatternLayout">
            <param name="ConversionPattern" value="%d{dd.MM.yy HH\:mm\:ss.SSS} %5p %c{1}:%L - %m%n " />
        </layout>
    </appender>

    <category name="com.mycomp.project.starter">
        <priority value="${project.client.log.level.starter}" />
    </category>
    <category name="com.security">
        <priority value="${project.client.log.level.security}" />
    </category>

    <root>
        <level value="ERROR" />
        <appender-ref ref="file" />
    </root>

</log4j:configuration>

When I start the Application I can set the log level through a ini file which can contain:

-Dproject.client.log.level.starter=INFO
-Dproject.client.log.level.security=DEBUG

What I would like to archive is, if the -Dproject.client.log.level.security=DEBUG is not set it should use ERROR.

How could I achieve this? I appreciate any help.