At a gathering this fall in Singapore, U.S. Climate Envoy John Kerry took a moment to assure his audience that the U.S. is taking climate change seriously.

"I'm happy to report that the United States has stepped up under President Biden's leadership," Kerry told the crowd at the Bloomberg New Economy Forum earlier this month.

Kerry often points to landmark climate legislation passed last year, the Inflation Reduction Act. The largest climate legislation ever passed in the U.S., it directs hundreds of billions of dollars to boost clean energy and speed the transition away from fossil fuels like oil and natural gas.

But many nations and climate advocates aren't impressed.

"There's just a trust deficit, in particular, with the U.S.," says Nisha Krishnan, climate director for the World Resources Institute's Africa office in Nairobi.

The U.S. has a mixed record when it comes to international climate negotiations. Historically, the U.S. is responsible for emitting more planet-warming greenhouse gasses than any other nation. And while U.S. emissions are falling, it remains a major polluter, emitting more each year than any country but China.

It's also sometimes a roadblock at negotiations. Former President Trump even removed the U.S. from the key Paris climate agreement, though President Biden later rejoined.

But for those reasons the U.S. is also indispensable in addressing climate change, especially when it's working with China.

Speaking in September at a climate ambition summit, United Nations Secretary General António Guterres pointed out a dynamic at the heart of climate negotiations. Rich countries caused most of the damage, primarily by burning fossil fuels like oil and gas to power their economic growth, while poorer countries are often suffering the worst consequences.

"Humanity has opened the gates of hell," Guterres said. "Many of the poorest nations have every right to be angry. Angry that they are suffering most from a climate crisis they did nothing to create."

Much of that anger comes down to money. Rich countries have promised to pay hundreds of billions of dollars to help poorer countries transition to cleaner energy and adapt to climate change. But Congress has resisted allocating enough money for those payments, in part because many lawmakers, including most Republicans, still oppose the Paris agreement.

"Even delivering on one of these promises for the U.S. would really, I think, help bolster its reputation," says Krishnan.

This year's climate talks have made some progress. On the first day of the COP28 climate summit in Dubai, negotiators finalized a new fund to help developing countries pay for damage caused by extreme weather events.

The host nation, the United Arab Emirates, committed $100 million to the fund, as did Germany. The United States pledged to work with Congress to commit $17.5 million.

But even as countries are frustrated with the U.S. for failing to live up to its commitments, there's an understanding that it remains essential to major breakthroughs.

"The Paris Agreement, for example, it really did take Obama to do all the backchannel diplomacy with China to be able to bring China to that table," says Naveeda Khan, chair of the Department of Anthropology at Johns Hopkins University. She recently published a book on climate negotiations between the U.S. and developing countries.

Ahead of the 2015 Paris Agreement, the Obama administration struck an important deal with China to limit greenhouse gas emissions, paving the way for the global deal.

As the world's two biggest economies and largest greenhouse gas emitters, international climate progress often depends on U.S. outreach to China, says Li Shuo, director of the China climate hub at the Asia Society Policy Institute.

"This relationship is a tone-setting relationship," Li says.

That relationship went into hibernation during the Trump administration and has been rocky under Biden, Li says. But this summer, it was rekindled, at least on climate issues. Earlier this month, climate envoys for both countries met in California, where they committed to a goal of tripling the deployment of renewable energy globally by 2030.

"The U.S. China Sunnylands statement will help improve or stabilize the politics at COP28. I think it is like an insurance policy to the U.N. climate summit," Li says. An insurance policy that, at least, the negotiations won't be a failure.

Nobody expects something on the scale of the Paris Agreement in Dubai. The negotiators could adopt the same commitment to triple renewable energy capacity and make more progress on climate finance issues. That may be enough to call it a success, considering the other geopolitical challenges in the world now, such as the wars in Ukraine and between Israel and Hamas.

But many people from developing nations want more.

"It's just high time that the United States has to come to terms with its role in global warming," says Denise Fontanilla, International Program Director at Institute for Climate and Sustainable Cities in the Philippines.

So far, U.S. efforts to cut greenhouse gas emissions are not enough to meet the nation's own commitments under the Paris Agreement. And the world is falling far short of the target to limit warming to 1.5 degrees Celsius (2.7 degrees Fahrenheit).

Fontanilla isn't expecting much from this climate summit.

"I certainly hope that the US will surprise me and the other people watching the negotiations," she says. "I would love to be proven wrong."