BEIJING (AP) — The world’s two biggest emitters of greenhouse gases are sparring on Twitter over climate policy, with China asking if the U.S. can deliver on the landmark climate legislation signed into law by President Joe Biden this week. U.S. Ambassador to China Nicholas Burns took to Twitter to say the U.S. was acting on climate change with its largest investment ever — and that China should follow. China’s Foreign Ministry responded with its own tweet: “Good to hear. But what matters is: Can the U.S. deliver?” The exchange is emblematic of a broader worry. U.S.-China cooperation is considered vital to the success of global climate efforts. With the breakdown in relations, some question whether the two sides can cooperate.