The United States, Australia, New Zealand and the Netherlands have said they were "disappointed" over the start of Japan's annual whale hunt off Antarctica and warned against violent clashes.
Japanese ships operating in the icy waters of the Southern Ocean have in recent years faced interference from the US-based militant environmentalist group Sea Shepherd, with repeated confrontations on the open seas.
The United States and its partners said while they supported the right to peaceful protest, any violence between whalers and demonstrators was unacceptable.
"The Governments of Australia, the Netherlands, New Zealand, and the United States jointly condemn any actions that imperil human life in the Southern Ocean," they said in a joint statement released by the US State Department.
"We are deeply concerned that confrontations in the Southern Ocean will eventually lead to injury or loss of life among protesters, many of whom are nationals of our countries, and whaling crews," they said.
"We remain resolute in our opposition to commercial whaling, including so-called 'scientific' whaling, in particular in the Southern Ocean Whale Sanctuary... and are disappointed about the recent departure of the Japanese whaling fleet for the Southern Ocean."
Commercial whaling is banned under an international treaty but Japan has since 1987 used a loophole to carry out "lethal research" on the creatures in the name of science.
Japan has claimed it is necessary to substantiate its view that there is a robust whale population in the world. It makes no secret of the fact that whale meat from this research ends up on dinner tables and in restaurants.
Anti-whaling nations and environmentalist groups routinely condemn the activity as a cover for commercial whaling.
Japanese ships cut short their 2010-2011 hunt in February, blaming interference from protesters.
The four nations hit out at Japan's claim it is carrying out research, saying they "wish to emphasise that lethal techniques are not required in modern whale conservation and management."
"We will continue to engage on this matter," the four nations pledged, reaffirming their commitment to the "global moratorium on commercial whaling."
The Japanese fleet aims to catch around 900 minke and fin whales this season, according to a plan submitted by the government to the International Whaling Commission.