newbie problem: load balancing

I want to achieve hierarchical mesh partitionning.
The idea was to use recursively metis for each level but for doing this I would like to know if that is possible to specify unbalanced partitionning. For example, I want to cut my mesh in two pieces one piece containing 60% of the elements, the other one the other 40%. Then I will iterate on each generated pieces.
Is that possible using metis ?

Thanks
G.