A bid to stop Japan from increasing whaling depends on just a few votes, Australian Environment Minister Ian Campbell said on Thursday.
Anti-whaling groups say Japan already kills too many whales
Members of the International Whaling Commission (IWC) are due to vote on the issue on 20 June.
Japan wants to resume commercial whaling and double the number of whales it catches for scientific purposes.
But Australia opposes the plan, and Mr Campbell has spent the last few weeks lobbying other nations for support.
Under a current international agreement, there is a moratorium on the commercial hunting of whales, although some can be killed for scientific research.
But the main whaling nations - Norway, Iceland and Japan - now want the ban partially lifted, arguing that stocks of some species have recovered enough to make hunting sustainable.
For many Japanese, whale meat is considered a delicacy
In addition, Japan wants to increase the number of whales it kills for scientific purposes - whales which can also then be consumed.
Under its research quota, Japan wants to start hunting fin and humpback whales and to raise its annual intake of minke whales.
Both issues are on the agenda of the IWC annual conference, which is currently taking place in Ulsan, South Korea.
Delegates are set to discuss a scheme to model how many whales can be killed without damaging overall numbers - the Revised Management System (RMS).
Mr Campbell is heading Australia's push to retain the status quo. He wants, instead, to persuade the IWC to create a Southern Ocean whale sanctuary.
The environment minister has spent the last few weeks travelling to various South Pacific island nations, hoping to gain their support.
"I think the cold, hard reality is that there are still one or two votes in this... We won't really know the answer until we get to Korea next week," Mr Campbell told ABC radio.
Japan has threatened to leave the IWC if the body votes against its plans.
Whale meat is seen as a delicacy in Japan, and officials in Tokyo maintain that the tradition is an important part of the nation's cultural heritage.