WELLINGTON, New Zealand: Antarctica's Ross Sea is often described as the most isolated and pristine ocean on Earth, a place where seals and penguins still rule the waves and humans are about as far away as they could be.

But even there it has proven difficult, and maybe impossible, for nations to agree on how strongly to protect the environment.

The United States and New Zealand have spent two years trying to agree on an Alaska-sized marine sanctuary where fishing would be banned and scientists could study climate change. But a compromise reached by diplomats from the two countries was rejected by senior New Zealand politicians this month.

The two countries will offer competing plans next month at an international meeting, but their lack of consensus makes any agreement less likely.