Speaking at a breakfast event with world mayors at global climate talks in Glasgow, he said with the most recent commitments made at COP26, around 65% of global GDP was now covered by implementable climate change plans.
"But that means 35% isn't. And we can't do it without that 35%," Kerry said.
"You don't get this done unless we are all in."
He also highlighted the importance of the world hitting its goal of halving global emissions by 2030 if it wanted to get to net zero emission by mid-century.
"2050 is also gone if you don't get 2030."
Kerry said negotiations were ongoing to bring China "to the table" and that the 1.5 degrees target would be imperilled if China went ahead with plans to build a 260 gigawatt coal-fired power station.