Some 125 world leaders are expected to commit to action on climate change at a UN summit Tuesday called to inject momentum in struggling efforts to tackle global warming.
The gathering will be the largest ever of governments and heads of states on climate change and the first of its kind since the Copenhagen summit collapsed in disarray in 2009.
US President Barack Obama is to outline his vision for limiting global warming, but key polluters China and India are sending lower-level representatives in a move seen as reducing the summit's authority.
"Action on climate change is urgent. The more we delay, the more we will pay in lives and in money," UN Secretary General Ban Ki-moon said this week.
While the summit is separate from the negotiations to be held under the UN Framework Convention on Climate Change (UNFCCC), Ban has urged leaders to come forward with offers and voice their commitment for a deal.
"Extraordinary forces are gathering together in New York to put political wind into the sails of the formal negotiations," said UN climate chief Christiana Figueres.
Diplomats point to the failure of the Copenhagen conference as a cautionary tale, underscoring the need to enlist political leaders now if the talks stand of chance of coming together in Paris in December 2015.
Tomorrow, about 100,000 demonstrators including Hollywood celebrity Leonardo DiCaprio and climate-change crusader Al Gore are to take part in a "People's Climate March" in New York to demand action from world leaders.
Billed as the largest climate change protest in history, the march will highlight the role of civil society in the push for climate change, just days before the UN summit welcomes not only world leaders, but also leaders from business, finance and mayors.
"We will see oil and gas companies come together with governments to announce what they're going to be doing on reducing methane and on investing in renewable energy," Figueres said.
The UN is seeking to limit global warming to two degrees Celsius over pre-industrial levels, but scientists say current emission trends could hike temperatures to more than twice that level by century's end.
Particular attention will be paid to China, with a much-awaited speech from Vice Premier Zhang Gaoli, the country's number three.
India's Prime Minister Narendra Modi is dispatching his environment minister to the summit, but diplomats will be paying attention to Modi's General Assembly speech four days later for any signs of movement on climate.
China and India have long argued that developed nations should shoulder the bulk of the responsibility -- and the cost -- for action on climate change and are resisting calls to commit to a binding agreement.
