Something

<path id="tomcat.classpath">
        <fileset dir="/usr/share/tomcat-5/server/lib/" includes="catalina-ant.jar" />
    </path>

    <taskdef name="deploy" classname="org.apache.catalina.ant.DeployTask">
        <classpath refid="tomcat.classpath" />
    </taskdef>

    <taskdef name="remove" classname="org.apache.catalina.ant.DeployTask">
        <classpath refid="tomcat.classpath" />
    </taskdef>