John Kerry, U.S. special presidential envoy for climate, is ending his trip to China without any concrete commitments to reduce emissions. 

“We came here to break new ground, which we think is important at this stage, and it is clear that we are going to need a little more work to be able to complete that task,” he said during a press conference Wednesday. 

He said that the two sides would “work intensively in the weeks ahead” on issues such as integrating renewable energy into the power sector as China largely relies on coal power.

Meanwhile, in remarks this week, Chinese President Xi Jinping said that the country’s commitments on climate change are “unwavering” but also said they “must be determined by the country itself, rather than swayed by others,” per the official People’s Daily newspaper. 

China is currently the world’s largest emitter of planet-warming gasses while the U.S is the second-largest, though the U.S. is the greatest historical emitter. The U.S. is currently seeking to reduce its emissions, while China has said that it intends for its emissions to peak in 2030.

The talks come after China halted its cooperation with the U.S. on issues including climate change for a few months last year after then-Speaker Nancy Pelosi (D-Calif.) visited Taiwan. They resumed talks on climate change in November.