* Small island states seen threatened by rising sea levels
* Commonwealth leaders to debate climate theme in Trinidad
* Meeting is last big summit before U.N. climate talks
* U.N. chief, French and Danish presidents also attending
By Pascal Fletcher
PORT OF SPAIN, Nov 26 (Reuters) - Commonwealth leaders will put the world's small island states at the frontline of the climate debate when they meet on Friday to press for an effective international pact against global warming.
Around half of the 53-nation Commonwealth group, mainly former British colonies, are island nations scattered across the world's oceans. Some of these fear they could be swamped or even literally wiped off the map in coming decades if sea levels rise as a result of worsening climate change.
Commonwealth leaders are holding a three-day summit in Trinidad and Tobago from Friday and host Prime Minister Patrick Manning said the meeting aimed to send a firm message in favor of cooperation to limit global warming ahead of U.N. climate change talks due in Copenhagen on Dec. 7-18.
"We hope to arrive at a political statement that can add value to the process that will culminate in Copenhagen next month ... what we can do is raise our voices politically," Manning told a news conference on Thursday in Port of Spain.
Commonwealth Secretary-General Kamalesh Sharma told Reuters the group would seek to give "voice and help" to tiny island nations like the Maldives in the Indian Ocean and Tuvalu and Kiribati in the Pacific, whose very existence would be threatened by increases in ocean levels.
Trinidad's Manning said small Caribbean states were also vulnerable to hurricanes, whose frequency could increase as global warming distorts and reshapes weather patterns.
The cases of these so-called "climate change frontline states" are seen adding urgency to calls for clear political commitments by industrialized powers to cut greenhouse gas emissions and so limit the rate of global warming that could dangerously increase sea levels in the future.
Manning said U.N. Secretary General Ban Ki-moon, French President Nicolas Sarkozy and Danish President Lars Lokke Rasmussen would join a special discussion session on climate change to be held by the Commonwealth leaders on Friday.
He said the Commonwealth's wide membership, bringing together wealthy industrialized nations like Britain, Canada and Australia with some of the world's smallest and most vulnerable states, made the group especially "reflective of world opinion" in the climate change debate.
Sharma said it would be up to the Commonwealth leaders to decide just how specific their call for action to fight global warming would be, but he added: "If I get very clear direction, the happier I'll be".
PRESSURE FOR COMMITMENT
Although most nations have given up hopes of agreeing to a final binding legal climate treaty text in Copenhagen, prospects for a broad political agreement have been brightened this week by public promises of greenhouse gas curbs by China and the United States, the world's biggest single emitters.
Both U.S. President Barack Obama and Chinese Premier Wen Jiabao have said they will attend the Copenhagen talks in what was seen as gestures of personal commitment to a climate pact.
But supporters of a strong and binding international agreement to fight global warming say more needs to be done.
"We need to press this week for presence and commitment in Copenhagen," said John Foster, a researcher with the North-South Institute, a Canadian non-profit organization that supports international development.
He said the Commonwealth, with its wide global reach, could act as a "bridging institution between resisters and supporters" of a climate deal.
The sought-after treaty to fight global warming, now expected to be adopted as a final text only next year, will replace the Kyoto Protocol that expires in 2012.
Commonwealth leaders in Port of Spain were also expected to discuss approving the admission of French-speaking Rwanda, whose President Paul Kagame has worked to bring his country into the English-speaking sphere in Africa after disagreements with France over events leading to the 1994 Rwandan genocide.
Some human rights groups have opposed Rwanda's admission on the grounds the country does not measure up to international standards for freedom and justice.
The Port of Spain meeting could also raise the possibility in the future of eventually readmitting Zimbabwe, which left the Commonwealth in 2003 after it was censured over a poll that re-elected President Robert Mugabe. Commonwealth observers had condemned his re-election as flawed. (For Factbox on the Commonwealth, click on [ID:nN24312730]) (For stories on climate change, click on [ID:nLL527527]) (Additional reporting by Linda Hutchinson-Jafar, Editing by Sandra Maler) ((pascal.fletcher@thomsonreuters.com; +1 305 810 2688))