Foreign Affairs Minister Murray McCully is defending the possibility of more changes to the proposal for a giant marine protected area in Antarctica's Ross Sea.
The original New Zealand-backed plan has been scaled down after several nations, including Japan and Norway, objected because of their fishing interests in the area.
The 25-nation Commission for the Conservation of Antarctic Marine Living Resources has begun new discussions in Tasmania.
Mr McCully says it will be difficult to get all 25 member states to agree on the complex plan and he is defending the possibility of further modifications as negotiators try to get the deal signed.
"Let's just wait and see, but it's important to us that we give our negotiators a chance to get 25 countries to agree, and that means they have to have some flexibility.
Mr McCully says he is optimistic of an international agreement, but not confident of one.