CAIRNS, Australia - The Pacific Islands Forum called on all nations Thursday to pledge a 50 per cent cut in their emissions of greenhouse gases by 2050 at UN climate change talks in December, bolstering appeals made a day earlier by seven of the region's most threatened islands.

"We call upon world leaders to urgently increase their level of ambition and to give their negotiators fresh mandates to secure a truly effective global agreement," the South Pacific leaders said in a joint statement Thursday.

Australian Prime Minister Kevin Rudd closed the three-day forum, warning that some tiny Pacific Island nations were in a race for national survival because of the threat posed by climate change, and sought urgent support from world leaders.

"This is not just a matter of importance, it is not just a matter of urgency, for many of them it is a matter of national survival," Rudd told reporters.

Seven countries in the 16-member forum had urged rich nations on Wednesday to make a minimum 45 percent cut in their polluting emissions by 2020.

Many scientists agree that carbon dioxide and other harmful gases are warming the planet and melting ice caps, gradually raising sea levels. Many Pacific countries have coral atolls no more than 10 feet (three meters) above sea level, and the rising oceans are already inundating some coastlines, polluting freshwater sources and killing off fruit-bearing trees and other crops.

Rudd, the new forum chairman, called the impact of this coastal devastation "sobering" because half the populations of the island countries live within less than a mile (1.5 kilometers) of their coastlines. He said the impact is "potentially huge if climate change is allowed to continue unabated."

The forum also called on states to cut global emissions to ensure they reach a peak no later than 2020, warning that "some habitats and island states face obliteration."

Rudd had set a target for Australia to cut its greenhouse gas emissions by up to 15 percent below 2000 levels by 2020, but says he might go deeper if a new pact is reached at the U.N. climate change talks in Copenhagen.

Pacific leaders also reaffirmed on Thursday Fiji's suspension from the forum on May 1 after coup leader and self-appointed Prime Minister Commodore Frank Bainimarama rejected the forum's repeated calls to return it to democracy.

The nations said in a statement that they "strongly condemned the actions of the Fiji military regime which have led to a severe deterioration in basic liberties and democratic institutions."

Fiji's regime eroded "the traditional pillars of Fijian civil society, including the churches and chiefs," in its abrogation of the constitution, imposition of media censorship and restrictions on freedom of assembly, the statement said.

The leaders also agreed to open negotiations on a Pacific Agreement on Closer Economic Relations, a free trade agreement covering the 16 states, by November. They decided Fiji would not participate in the talks but would be kept informed of their progress.

Newly appointed Fiji Foreign Minister Inoke Kubuabola, speaking in Suva, said Thursday that the forum's selective invitations to Fiji "as and when it suited them" were a poor reflection on its leadership.

Meanwhile, New Zealand announced Thursday a package of economic and expert assistance for island countries to support their participation in the trade talks.

"Trade remains a key driver for economic development in the Pacific and we want to see the Pacific producing and trading more successfully with New Zealand, Australia and other trading partners," Prime Minister John Key said at the close of the summit.

The forum comprises Australia, Cook Islands, Federated States of Micronesia, Kiribati, Nauru, New Zealand, Niue, Palau, Papua New Guinea, the Marshall Islands, Samoa, Solomon Islands, Tonga, Tuvalu and Vanuatu.