President Joe Biden told the COP27 conference Friday the "very life of the planet" is at stake in the climate crisis and gave an assurance the United States is on track to slash carbon emissions.
"The climate crisis is about human security, economic security, environmental security, national security and and the very life of the planet," he told an audience at the conference in Egypt.
Biden said the United States is "on track" to achieve its pledge of cutting emissions 50-52 percent below 2005 levels by 2030.
Biden, who was spending only a few hours in the resort of Sharm el-Sheikh before travelling on to ASEAN and G20 summits in Asia, challenged other countries to do more to cut carbon emissions in the hope of bringing global warming under control.
"Every nation needs to step up. At this gathering, we must renew and raise our climate ambitions," he said in a speech that lasted about 22 minutes and was briefly interrupted by unidentified people in the crowd making howling noises.
"It's a duty and responsiblity of global leadership. Countries that are in a position to help should be supporting developing countries so they can make decisive climate decisions -- facilitating their energy transitions, building a path to prosperity compatible with our climate imperative."
"The United States will meet our emissions targets," he said.
"We're living in a decisive decade -- one in which we have an opportunity to prove ourselves and advance the global climate fight," Biden said on Twitter before his arrival at the climate conference.
"Let this be a moment where we answer history's call. Together," said the US leader, who skipped a two-day summit of some 100 world leaders at COP27 earlier this week that coincided with the US election.
White House National Security Advisor Jake Sullivan said Biden is underscoring "the need to go further, faster, to help the most vulnerable communities build their resilience" and push major economies to "dramatically" cut emissions.
"How long do we have to sit around to wait before we say, 'Hey let's get really serious'," US climate envoy John Kerry earlier told a COP27 panel.
President Biden came as the White House issued a statement "doubling the U.S. pledge to the Adaptation Fund to $100 million and announcing over $150 million in new support to accelerate the President’s Emergency Plan for Adaptation and Resilience (PREPARE) efforts across Africa."
Kerry presented earlier this week a public-private partnership aimed at supporting the transition to renewable energy in developing nations and based on a carbon credit system.
But the plan has been panned by activists wary of firms using these to "offset" their carbon emissions.
"The world needs the United States to be a climate leader in our fight for climate justice," prominent Ugandan climate activist Vanessa Nakate, a 25-year-old Goodwill Ambassador for UNICEF, told AFP.
Germany's climate envoy, Jennifer Morgan, said Biden's attendance at COP27 was a "very good sign".
"I think it reassures countries, people, that the United States at the highest level takes this issue incredibly seriously and we need that," Morgan told reporters.
Biden will spend only a few hours at COP27 in the Red Sea resort of Sharm el-Sheikh, three days after US midterm elections that have raised questions about what the result could mean for US climate policy.
COP27 talks have been dominated by the need for wealthy polluters to stop stalling on helping developing countries green their economies and prepare for future impacts -- as well as calls to provide financial help for the damage already being caused by climate-induced catastrophes.
Biden pledged to contribute $11.4 billion to a $100 billion per-year-scheme through which rich countries will help developing ones transition to renewable energies and build climate resilience.
But Democrats would have to rush it through Congress before climate-sceptic Republicans take office in January.
"We're going to be pressing for passage of the appropriations bills," US lawmaker Kathy Castor, who chairs a special climate crisis committee in the House, told AFP.
"Hopefully Republicans in the Congress will not block it," she said.
The United States has for years resisted attempts to establish a "loss and damage" fund in which rich polluters would compensate developing nations for the destruction from climate-related disasters.
Emerging countries successfully put the issue on the official COP27 agenda, with fraught negotiations likely before talks end on November 18.
Biden also met with Egyptian President Abdel Fattah al-Sisi and discuss the human rights situation in the country, where the case of jailed dissident Alaa Abdel Fattah was raised by other leaders earlier this week.
Ahead of his trip, the White House expressed "deep concern" for the jailed British-Egyptian activist, who is on a hunger strike.
After COP27, Biden will head to an ASEAN regional summit in Cambodia at the weekend before travelling to Indonesia for G20 talks.
Biden may have a chance to revive cooperation with China when he meets President Xi Jinping at the G20.
US-Sino cooperation has been crucial to the fight against global warming, but Beijing cut off climate talks with Washington after US House Speaker Nancy Pelosi visited Taiwan in August.