BEIJING, China (AP) — The world’s two biggest emitters of greenhouse gases are sparring on Twitter over climate policy, with China questioning whether the US can deliver on the landmark climate legislation signed into law by President Joe Biden this week.

“You can bet America will meet our commitments,” US Ambassador to China Nicholas Burns tweeted in response on Wednesday, using a national flag emoticon for America. He called on China to resume suspended climate talks, writing, “We’re ready.”

The punchy exchange, part of a longer back and forth on Twitter, is emblematic of a broader worry: US-China cooperation is widely considered vital to the success of global efforts to curb rising temperatures. With the breakdown in relations over Taiwan and other issues, some question whether the two sides can cooperate.

After Congress passed the Climate Bill last Friday, Burns took to Twitter over the weekend to say the US was acting on climate change, with its largest investment ever and that China should follow.

On Tuesday night, China’s Foreign Ministry responded with its own tweet: “Good to hear. But what matters is: Can the US deliver?”

The verbal skirmish grew out of China’s suspension of talks with the US on climate and several other issues earlier this month as part of its protest over a visit to Taiwan by a senior American lawmaker, House Speaker Nancy Pelosi.

Climate has been one of the few areas of cooperation between the feuding countries. US officials criticised China’s move, with Secretary of State Antony Blinken saying it “doesn’t punish the United States — it punishes the world”.

Asked to respond, Chinese Foreign Ministry spokesperson Zhao Lijian called on the US last week to “deliver on its historical responsibilities and due obligations on climate change and stop looking around for excuses for its inaction”.

The ministry later tweeted some of his answer, and Burns responded four days later with his tweet on the US Climate Bill. Using the abbreviation for the People’s Republic of China (PRC), he ended with, “The PRC should follow+reconsider its suspension of climate cooperation with the US.”

China elaborated on its “Can the US deliver?” message with a second tweet suggesting that the US meet rich country pledges to help poorer countries cope financially with climate change and lift sanctions imposed last year on solar industry exports from China’s Xinjiang region because of allegations of forced labour.

The Twitter battle highlights a perception divide between the long-standing superpower that wants to lead and the rising power that no longer wants to feel bound to follow anyone else’s direction.

The decision by former President Donald Trump to pull the US out of the Paris Climate Accord — reversed by Biden after he took office last year — dealt a blow to American credibility on the issue.

A Chinese expert praised parts of the US legislation but said it is overdue and not enough.

“Although there are some breakthrough achievements in the Bill, I am afraid it can’t re-establish US leadership on climate change,” said Teng Fei, a professor at Tsinghua University’s Institute of Energy, Environment and Economy.

US climate envoy John Kerry has been pressing China to set more ambitious climate goals. China has responded that its goals are realistic, given its development needs as a middle-income country, while the US sets ambitious goals that it fails to achieve.