How can we add ant-claspath before the system.classpath?

I am compiling the java code by using below ant target

classpathref="compile.path" ...>

it is adding 'compile.path' to the existing 'system.classpath'.
But i want to add 'compile.path' first and 'system.classpath' should be last.

Please let me know how can this could be done?

Thanks in advance
Sankar