District health boards in Auckland are urging Diagnostic Medlab Limited to work with a new operator in the region.
Labtests Limited is to take over the $560 million contract on 7 September.
But the DHBs say DML has not met Labtests and is not likely to.
Labtests describes its progress as pleasing and wants to take over in stages from August.
The DHBs say DML's ongoing opposition is complicating the changeover.
The contract involves testing up to 36,000 blood and other samples per day for 9000 people.