The New Zealand Government has joined Australia, the Netherlands and the United States to condemn whaling in the Southern Ocean and any potential violence there.
Three ships, led by the 720-tonne Yushin Maru, set sail from Shimonoseki in western Japan last week with the aim of catching about 900 minke and fin whales.
The joint statement says the countries are deeply concerned that confrontations in the Southern Ocean will eventually lead to injury or death among protesters and whaling crews.
The statement condemns dangerous or violent activities and is calling on the masters of all vessels involved to strictly observe international rules on avoiding collisions.
Foreign Affairs Minister Murray McCully said last week there were no current plan to send a vessel to monitor the whaling, but the situation will be kept under review.
Commercial whaling is banned under an international treaty but since 1987 Japan has used a loophole to carry out "lethal research" on the mammals in the name of science.
Japan claims it is necessary to substantiate its view that there is a robust whale population in the world.
