Brown discussed his plans in a telephone interview after U.S. President Donald Trump announced he would exit the Paris international climate accord. Brown vigorously opposes the withdrawal and has been working with states and provinces around the world to set voluntary agreements to address global warming.

The governor heads to China on Friday for meetings focused on climate change.

California has the largest U.S. carbon trading system and frequently has hosted officials from China. China has launched seven pilot regional trading schemes and plans to roll out a nationwide market this year. However the launch faces delays amid unreliable data and other regulatory problems, a government researcher said recently.

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California’s system, which is known as “cap and trade” already is linked to Canada’s Quebec market.

“I think that is a heavy lift to include Chinese provinces but we are definitely taking that possibility very seriously,” Brown said.

“We want to make sure it has full integrity and know exactly what’s going on. And we can’t say that today,” he said. “Maybe we don’t put it right in the same cap and trade regime, maybe some parallel regime,” he added. “I am going to discuss that with the highest officials in China this week.”