Does the landlord have the right to increase the rent for a lease assignment

My landlord has given me permission to do a lease assignment for the last two months of the lease as we need to move back to Australia. The tenant is already approved by the building as they are current tenants with a lease that is expiring. The catch is that the landlord wants to increase the rent by $600 a month for the reassignment. Is this allowed. Do I have any recourse.