AFP - The Commonwealth is trying to shape the direction of upcoming climate talks in Copenhagen by inviting top outside leaders to a weekend summit here, host Trinidad said on Thursday.

UN chief Ban Ki-moon, French President Nicolas Sarkozy and Danish Prime Minister Lars Loekke Rasmussen have all been invited because "there was some concern about the way negotiations were going ahead of Copenhagen next month," Prime Minister Patrick Manning said.

He told a news conference he put the three extra seats at the table after consulting with Britain and the United Nations -- and was "aware of talk" of US President Barack Obama also being invited, though that ultimately went nowhere.

The aim of including the other speakers was to bolster the weight of a political statement from the Commonwealth -- whose 53 nations account for a third of the planet's population, or two billion people -- ahead of the December 7-18 UN climate change talks in the Danish capital, he said.

"We feel it can have some influence on the way decisions go in Denmark," he said.

His statements reflected international concern that the climate change meeting could fall far short of its goal of fixing substantial greenhouse gas emission cuts.

Those doubts, sharper several weeks ago when the invitations were extended, have been allayed a little by Obama saying on Wednesday he would attend Copenhagen, and China pledging on Thursday to cut carbon dioxide emissions by up to 45 percent in 2020, based on per unit of gross domestic product calculated at 2005 levels.

However the practical contribution the world's two biggest greenhouse gas polluters will make to the bottom line of any treaty remained questionable, especially as both the United States and China face strong domestic pressures to favor their national economies over the environment.

Obama's offer to curb US emissions by 17 percent from 2005 levels by 2020 is conditional on approval from a reluctant US Congress, while an official statement in China stressed the "enormous pressure and special difficulty in controlling greenhouse gas emissions" it faced.

The Commonwealth summit is the last major gathering of world leaders before the UN climate conference in Copenhagen.

Organizers said it was important because it gave underrepresented countries a chance to speak alongside richer or more powerful nations.

"It allows the world's small countries to have their voice heard," Commonwealth secretariat spokesman Eduardo del Buey told AFP.

Britain's Queen Elizabeth II, the titular head of the Commonwealth, will open the Trinidad summit early Friday before handing the microphone over to other officials, including Ban, Sarkozy and Rasmussen.

She arrived in Trinidad's capital of Port of Spain on Thursday, just after Indian Prime Minister Manmohan Singh.

Ban was expected later Thursday.

Sarkozy was to fly in from another climate change conference in the northern Brazilian city of Manaus on Thursday that turned out to be something of a flop.

The Manaus meeting had been designed to bring together the heads of state of the countries encompassing the vast Amazon forest -- including Guiana, a South America territory administratively considered a part of France.

But in the end only three of the nine presidents turned up: Sarkozy, Brazil's Luiz Inacio Lula da Silva, and Guyana's President Bharrat Jagdeo.

The leaders of Bolivia, Colombia, Ecuador, Peru, Suriname and Venezuela all canceled, most citing scheduling problems, and sent their foreign ministers or other, more junior officials instead.