President Xi Jinping of China pledged on Tuesday that his country would adopt much stronger climate targets and achieve what he called "carbon neutrality before 2060." If realized, the pledges would be crucial in the global fight against climate change.

The announcement, made at the annual meeting of the United Nations General Assembly, is significant because China is currently the top producer of greenhouse gas emissions. What the country does to curb its emissions, therefore, is crucial to slowing down global warming on the whole.

Todd Stern, the chief United States negotiator at talks for the 2015 Paris Agreement, called the carbon neutrality target "big and important news."

"The closer to 2050 the better," Mr. Stern said.

The timing of the announcement was equally notable, coming so close to United States elections in which climate change has become increasingly important to voters.

President Trump has pulled the United States out of an international agreement aimed at slowing down climate change. His challenger, Joseph R. Biden Jr., has pledged to rejoin the accord and promised to spend $2 trillion to slash emissions and address the effects of climate change.

"It demonstrates Xi’s consistent interest in leveraging the climate agenda for geopolitical purposes," said Li Shuo, a China analyst for Greenpeace.

In his speech, Mr. Xi called on countries to "achieve a green recovery of the world economy in the post-Covid era."

"Humankind can no longer afford to ignore the repeated warnings of nature and go down the beaten path of extracting resources without investing in conservation, pursuing development at the expense of protection, and exploiting resources without restoration," Mr. Xi said.

Not only was that a sharp counterpoint to the Trump administration’s expansive rollbacks of environmental protections, but also a way to deflect criticism of China’s own handling of the coronavirus epidemic.

"The contrast between Xi’s speech and Trump’s speech is stark," said Joanna Lewis, a Georgetown University professor who follows China’s climate policies. "While Trump’s speech blames China for the world’s problems, Xi’s speech calls for global response and highlights China’s contributions."

But his remarks were less than precise on how and how quickly China would ratchet up its climate policies.

First, while Mr. Xi said China would peak its emissions of greenhouse gases "before 2030," he did not specify how soon. In the past, China had said its peak emissions would come "around" 2030, after which its total emissions would begin to decline. China is on track to reach peak emissions within the next decade.

Second, by saying China would aim to achieve carbon neutrality before 2060, Mr. Xi left vague exactly when that key threshold would be reached. There is scientific consensus that the world must reach carbon neutrality, sometimes referred to as net-zero emissions, by 2050 in order to have a reasonable chance of averting the worst climate hazards.

"This announcement therefore buys China some time," Dr. Lewis said, "since the results of the U.S. presidential election are certainly one factor China is considering as it finalizes its climate plan."

China is the world’s largest consumer of coal, even as it dominates clean energy technology, producing more solar panels and wind turbines than any country in the world. It is also the world’s largest manufacturer of electric cars and buses. Whether and how China transitions away from fossil fuels to renewable energy could become clearer when it issues its next five-year economic plan, which will guide the country’s economic trajectory from 2021 through 2025.

Climate change stands to affect the supply of food and water in China, while sea level rise threatens densely populated industrial cities along the country’s coast. Average temperatures have risen faster in China than the global average between 1951 and 2017.