The former army chief leading the Pike River recovery mission says there is an "over 90 percent" chance of getting back into the mine.
Dave Gawn told Newshub a manned re-entry is "truly do-able".
"I put it at higher than 90 percent from everything I have been told, from everything I understand."
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Mr Gawn was Chief of the New Zealand Army from 2013-2015, and is now chief executive of the Pike River Recovery Agency (PRRA).
"Everything that I have discussed with experts from around the world suggests that this is truly do-able," he said.
Mr Gawn said the agency had a plan to get in was currently preparing a final risk analysis before getting sign-off from the Government.
"Once we've done that i think we will find we can do this safely and effectively to recover the full drift."
Mr Gawn said it was "not impossible" they would find bodies in the drift, which is the mine's 2.3km access tunnel.
"In terms of what I've read and understand, it's less likely that there are any bodies in the drift - it's not impossible, but it's less likely."
Mr Gawn had a military career spanning almost 40 years - 36 years in the Army, then two years in Israel - as Head of Mission for the United Nations overseeing peace-keeping operations.
He said the Pike River recovery, which has a $23 million budget, was different to a battlefield because there were no time pressures.
"It's not time-bound, and from the outset I've always said the next stage will be determined by being successful in the previous task - that is quite different from the military."