Overseas visitors could face new charges to visit national parks.
Associate Tourism Minister Paula Bennett says the work is underway to look at ways of extending charging of foreign visitors to national parks.
About 3.2 million visitors come from overseas a year and of those on holiday here about half go to national parks, the minister said at the Trenz travel event in Rotorua
"As those numbers grow you can see increased pressure," she said.
"We certainly aren't ruling anything in or out at the moment - it's something to discuss and not something that would be done lightly."
She said she was working with Conservation Minister Maggie Barry on the issue.
Foreign visitors did pay for using some tracks and huts, as do New Zealanders.
Bennett said charging for access was not on the cards.
The government was warned in 2012 that increased demand on 14 national parks from international tourists, could lead to "negative outcomes for New Zealanders".
A briefing from the Ministry of Economic Development said access to major Government-owned tourism assets was "often free or heavily subsidised".
"So increasing demand from non-residents in such cases may not translate into value for New Zealand."
Bennett said so far discussions were "broad."
Labour's new tourism spokesman Kris Faafoi said any new charging would have to be carefully implemented given challenges collecting new fees.
"At this early stage for the operational side is a difficult mechanism."
One option was a one-off pass visitors could buy when the enter the country but pricing would have to appropriate for different travel markets.