U.S. President Barack Obama has told 150 world leaders at a crucial climate summit in Paris that they need to "rise to the moment" and show the world that nations share a sense of responsibility to battle climate change.
Speaking to the United Nations conference on November 30, Obama said world leaders should build a climate agreement on ambition and "regularly updated targets."
He said the United States embraces the responsibility to do something about cilmate change as the world's second largest emitter of greenhouse gasses, which are blamed for causing global warming.
Obama also said the U.S. would pledge new funds to help vulnerable countries tackle the impact of climate change.
Earlier on November 30, French President Francois Hollande opened the Paris climate summit by calling upon world leaders at the event to create a strong climate agreement.
Hollande told the summit the stakes of an international meeting have never been so high.
Pope Francis said it is "now or never" for the world to come to a climate agreement because the situation is "borderline suicide."
But Indian Prime Minister Narendra Modi said in Paris that developing countries still need oil, coal, and other carbon-producing energy sources.
"Climate justice demands that [with] the little carbon space we still have, developing countries should have enough room to grow," he said.
India, a developing country with some 1.25 billion people, is heavily dependent on coal for its energy.
President Xi Jinping of China -- the world's largest emitter of carbon into the atmosphere -- said resolving the issue of climate change "is a shared mission for mankind."
But he added that delegates at the conference must find "an equitable and effective global mechanism on climate change" that would allow for "sustainable development at a high level."
Meanwhile, United Nations Secretary General Ban Ki-moon told the gathering the world needs to go “much faster” and “much further” in order to reach the target of limiting global warming to two degrees Celsius by the end of the century.
The UN conference, known as COP21, is aimed at securing a long-term agreement by negotiators from 196 countries that would limit emissions of the greenhouse gases blamed for warming the planet.
The conference will run from November 30 to December 11 under tight security after deadly terrorist attacks in the French capital earlier this month.
The U.S., Chinese, and Russian presidents as well as India’s prime minister are among the 147 heads of state and government attending the conference amid a growing sense of optimism that an agreement can be secured.
"I'm optimistic about what we can achieve -- because I've already seen America take incredible strides these past seven years," U.S. President Barack Obama said in a Facebook post released as he took off from Washington.
WATCH: Putin Calls For Binding Emissions Targets
"What makes this gathering different is that more than 180 nations have already submitted plans to reduce the harmful emissions that help cause climate change," he added.
Important meetings between global leaders also were expected on the sidelines of the conference about issues like fighting terrorism and the Islamic State militant group.
But Kremlin spokesman Dmitry Peskov said President Vladimir Putin will not meet with Turkey’s President Recep Tayyip Erdogan in Paris on November 30.
In the midst of a dispute between Russia and Turkey over the November 24 downing of a Russian fighter jet near Turkey’s border with Syria, Peskov said no contacts with Turkish officials were planned.
But Peskov said it was likely that Putin and Obama would talk on the sidelines of the climate conference.
The leaders were expected to make several announcements on November 30 to boost the fight against global warming.
Indian Prime Minister Narendra Modi, for instance, was due to announce a global alliance that aims to bring together 100 solar-rich countries in tropical regions to expand the availability of electricity from the Sun.
Obama and Hollande plan to join Bill Gates, the world’s richest man, to announce new efforts to dramatically increase spending around the globe on developing clean energy technologies that can help reduce carbon emissions.
The last global climate treaty, the 1997 Kyoto Protocol, required only rich countries to reduce emissions, and some of the world's biggest emitters didn't take part.
After years of struggling negotiations marked by the failure of a previous summit in Copenhagen in 2009, differences remain between the parties.
The European Union and many developing countries are calling for a legally binding international treaty to reduce emissions, but the United States refuses to sign up to such a document as there would be little chance of getting it through a Republican-dominated Senate.
According to Obama, the goal in Paris is a "long-term framework" for global reductions, with "targets set by each nation, but transparent enough to be verified by other nations."
How and when countries should review their goals, and set more ambitious ones, must still be hammered out.
And if a signed deal now appears likely, so too is the prospect that it will not be enough to limit the rise of the world’s average temperature to 2 degrees Celsius above pre-industrial levels.
The 48 members of the Least Developed Countries group at the climate talks say that anything more than 1.5 degrees would be catastrophic for them, and call for “an ambitious, robust, and binding climate deal that does not leave behind the most vulnerable among us."
Some countries also want to talk about decarbonizing the world by the middle or end of this century, which major oil producers reject.
Another issue in dispute is money: rich nations have promised they would give $100 billion by 2020 to the developing world to tackle climate change, but the cash has been slow in coming.
There is no agreement yet about what will happen after 2020, with wealthy countries wanting that a larger number of countries share the burden of cutting carbon.
According to the London-based International Institute for Environment and Development (IIED), the world’s 48 poorest countries will need to find $93 billion a year from 2020 to achieve their plans to reduce emissions and adapt to the effects of climate changes.
On November 29, hundreds of thousands of people from Australia to Paraguay took part in demonstrations to demand leaders take firm action against global warming.
Thousands of demonstrators gathered in central Paris and formed a human chain along the route of a long-planned protest march, which was banned under state-of-emergency rules introduced after gunmen and suicide bombers killed 130 people in and around the French capital on November 13.
French authorities detained 208 people and 174 were kept in custody following clashes between a few hundred protesters and police.
Hours before the official opening of the UN climate conference, Obama paid respects to the victims of the terrorist attacks.
Obama, accompanied by Hollande and Paris Mayor Anne Hidalgo, laid flowers at the Bataclan concert hall, the bloodiest scene of the attacks, as helicopters flew overhead.
With reporting by AP, AFP, Reuters, and the BBC