Energy Secretary Rick Perry invited China to compete with the U.S. on clean energy technology this week, in the wake of President Trump’s decision to withdraw from the Paris climate agreement.

“I hope China will step in and attempt to take the mantle away” from America, Perry told reporters in Tokyo on Monday, Bloomberg reports. “It would be a good challenge for them.”

Business leaders repeatedly warned the Trump administration that pulling out of the climate treaty could put the U.S. at a disadvantage in the global race to create and deploy greentech solutions. There are concerns about curbing clean energy research and development within the U.S., and about the ability for American companies to win contracts abroad.

However, Perry insisted that the U.S. would remain the world leader on clean technology.

“Those that would say, ‘well you created this void where China is going to take over’ — no, we’re not stepping back and we haven’t created a void,” the secretary said. “The United States is not backing down from its role as a leader in cleaning up the planet.”

Perry visited the Fukushima Dai-ichi nuclear plant north of Tokyo on Sunday, which was destroyed during a 2011 earthquake and tsunami. He offered U.S. support in decommissioning the plant, which could take decades, while touting the benefits of nuclear power.

“If you’re a millennial, and you care about the environment of where you live locally and of the world, then you need to be for nuclear energy,” Perry said, according to the Associated Press. “Zero emissions.”

Laboratories within the U.S. Department of Energy are researching new ways to harness nuclear power, from small modular reactors to fusion, the DOE secretary said. Perry stated earlier this year that maintaining U.S. leadership in nuclear energy research and protecting U.S. nuclear power plants is a matter of national security.

The DOE is currently conducting a review of the U.S. energy system, which is expected to show why baseload resources like nuclear and coal are key to maintaining grid reliability. Many energy stakeholders fear, however, that the study is unfairly biased against alternative resources, like wind, solar and energy storage.

Secretary Perry attended an energy conference China today, following his trip to Japan, where he spoke about carbon capture and storage as “a critical low-carbon technology,” the New York Times reports. Perry did not discuss the Paris Agreement in Beijing; nor, apparently, did he meet with President Xi Jinping.

California Governor Jerry Brown did meet with the Chinese president today, though. It is unusual for Xi to meet with a governor-level official from another country. Yet Brown and Xi met for 45 minutes, discussing the importance of expanding cooperation on clean energy technology, innovation and trade.

Brown also signed an agreement with China’s Minister of Science and Technology to deepen cooperation on the development of green technology.

“California is the leading economic state in America, and we are also the pioneering state on clean technology, cap and trade, electric vehicles and batteries, but we can’t do it alone,” said Governor Brown during his meeting with President Xi. “I have proposed that California will cut its greenhouse gases 40 percent below 1990 levels and that we’ll have 50 percent of our electricity from renewables. To keep that goal, we need a very close partnership with China — with your businesses, with your provinces, with your universities.”

California’s political leaders have been vocal opponents of President Trump’s energy and environment policies. Governor Brown told E&E News last week that with the U.S. withdrawal from the Paris accord, China is the world’s “hope” on combating climate change.

“America was a leader with China, and now America’s gone AWOL under Trump, and China’s the leader,” he said. “China’s the hope, and that’s why I’m going to China to work with them on a sensible climate change strategy.”

Climate change was not a factor in President Trump’s decision to leave the climate deal, according to EPA Administrator Scott Pruitt. In a Tuesday interview on Morning Joe, Pruitt said he did not discuss climate change with President Trump while deliberating the Paris decision. Rather, the decision was made solely on the “merits and demerits” of the accord, he said.

“We took weeks evaluating this, and he put America first with respect to this decision,” said Pruitt.