United Nations Secretary-General Ban Ki-Moon says tackling climate change will mean changing the global economy, and placed the onus on the U.S. and China to drive that change in the months after Paris.

"Our goal now must be nothing less than a radical change of the global economy," the secretary-general said Thursday in opening a major climate summit in Washington. The U.S. and China, the two largest greenhouse gas emitters, "are pivotal for this task," he said.

The secretary-general wasn't specific on what radical change would mean, but World Bank President Jim Yong Kim later suggested it was important in the wake of the Paris agreement for countries to begin establishing regional carbon markets, while also taking steps to reduce pollution from cars and trucks.

Establishing regional carbon markets is something the administration tried to encourage states to do under its Clean Power Plan regulations. But for much of the country the idea is contentious, especially with the Clean Power Plan being halted by the Supreme Court in February until all court challenges against it are heard.

Nevertheless, the secretary-general said the two-day summit in Washington is meant to push industry and nations to make good on meeting the goals of last year's landmark climate agreement in Paris.

"Across this country and around this world we are seeing the emergence of the clean energy, climate-resilient society of tomorrow," he said.