Prime Minister John Key is expressing doubts about the viability of retrieving the bodies of 29 men who died in the Pike River mine disaster.
The miners and contractors were killed in a series of explosions at the West Coast mine which began on 19 November last year. No one has been in the mine since, as it had been deemed too dangerous.
On Monday, police, the receivers and the Mines Rescue Service agreed to investigate options for a re-entry operation.
Mr Key said on Tuesday the Government has not ruled out contributing financially to a feasibility study on the viability of a recovery operation, but he has doubts about its chances of success.
"If you look internationally, typically these things are dangerous, complex and take a very long period of time. And the international mine inspectors we've spoken to have said in some instances, you can never get in mines."
Mr Key says the main concern is the safety of anyone entering the mine.
Labour Party leader Phil Goff says everything humanly possible has to be done to get the men's remains back to their families.
Mr Goff says the Prime Minister promised that a recovery would happen and he should follow through with this.
The first obligation falls on the Pike River company or the receivers, but the Government should be the back-up, he says.
Meanwhile, an international mine safety expert says going into the collapsed mine will be very difficult.
David Feickert says rescue crews would have to feel their way along the tunnel, carrying breathing gear and always alert for any new rock fall which could trap them inside the mine.