WASHINGTON >> Secretary of State John Kerry said Tuesday the U.S. and China must work together to stave off a global catastrophe from climate change, as he appealed for greater cooperation between the two world powers despite strains between them over cyber theft and maritime security.

Kerry heads to Beijing this week, to set the stage for a visit by President Barack Obama for a regional summit and talks with Chinese President Xi Jinping. That will be first leg of a three-nation swing through Asia, intended to underscore the president’s commitment to the region.

“The US-China relationship is the most consequential in the world today. Period. And it will do much to determine the shape of 21st century. That means that we have to get it right,” Kerry said in an address on U.S.-China relations at the Johns Hopkins School of Advanced International Studies in Washington.

But Kerry also made clear the U.S. wouldn’t back down in its differences with China on cyber espionage, human rights violations and maritime security in the South China Sea, where China has disputes with several of its Southeast Asian neighbors that could spark conflict.

On the positive side of the ledger, Kerry praised China’s help on combating nuclear proliferation by Iran and North Korea and welcomed a growing Chinese role for the stability of Afghanistan as the U.S. draws down its forces after 13 years of war. He commended China for committing $130 million in aid to combat Ebola in West Africa, and to deploy a military unit to Liberia.

“That’s global leadership,” Kerry said.

He made the case in stark terms for greater cooperation between the U.S. and China on climate change, which he said presented not just an environmental threat to the world, but one to the economy, health and security as people compete for food and water resources.

“That will change the nature of security and conflict in the world. That’s the reality of what we’re up against. That’s why it is so imperative that the United States and China lead the world with genuine reductions and put us on a path to real progress,” Kerry said.

The secretary said that together, the U.S. and China, the world’s two largest economies and energy consumers, account for nearly 50 percent of global emissions.

Kerry was departing Washington Tuesday. But before he arrives in China, he’ll be stopping in Paris, where he’ll meet with French Foreign Minister Laurent Fabius on Wednesday to discuss a range of issues including the Islamic State group, Ebola, and Ukraine.

In Beijing, Kerry is due to meet top diplomats from Australia, Indonesia, Japan and New Zealand and, of course, China. He will then will make a brief detour to Muscat, Oman, to meet with negotiators on Iran’s nuclear program, before returning to Beijing for Obama’s arrival for an economic summit of Asia-Pacific leaders starting Monday. The president will later travel to Myanmar and Australia.