Leaders of Pacific island nations expressed strong concerns over the release of treated radioactive water from Japan's wrecked Fukushima nuclear plant into the Pacific Ocean during a regional summit through Friday, according to Cook Islands Prime Minister Mark Brown.

Brown, who currently chairs the Pacific Islands Forum, said Thursday there were "strong concerns" raised by "our forum leaders for the significance of potential threats of contamination to the health and security of the blue Pacific."

The bloc's 18 members have expressed differing views on the treated wastewater discharge from the Fukushima Daiichi nuclear power plant, which began in late August, after extensive dialogue between the member states and Japan.

Speaking to reporters on Aitutaki in the Cook Islands, Brown added that the bloc's leaders "also recognize the sovereignty of each of our members to determine their own national positions on this critical issue."

The Cook Islands has said it believes that the water release meets international safety standards, with other forum members such as Australia, Fiji and New Zealand respecting the findings of a review conducted by the International Atomic Energy Agency in July that concluded the discharge plan adhered to global safety standards.

The prime minister of the Solomon Islands, which has developed close ties with China in recent years, denounced the discharge during a U.N. General Assembly session in September.

During the meeting, the leaders also raised the prospect of reviewing the terms of the South Pacific's 1985 nuclear weapons-free zone agreement, the Treaty of Rarotonga, in light of Australia's plans to acquire nuclear-powered attack submarines from the United States, as well as discussing strategies to tackle climate change, Brown said.

The leaders' meeting began in the Cook Islands Monday, with the main talks taking place Wednesday and Thursday on Rarotonga, the country's most populous island, and Aitutaki.

The Pacific Islands Forum comprises Australia, the Cook Islands, Micronesia, Fiji, French Polynesia, Kiribati, the Marshall Islands, Nauru, New Caledonia, New Zealand, Niue, Palau, Papua New Guinea, Samoa, the Solomon Islands, Tonga, Tuvalu and Vanuatu.

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