WASHINGTON – Donald Trump was succinct when asked how the United States should respond to climate change. “It’s not a big problem at all,” the leader in opinion polls for the Republican presidential nomination told a radio talk show host on Monday. “If you look at China, they’re doing nothing about it.”

Later in the week, however, Chinese President Xi Jinping agreed to take new measures on climate change. Standing alongside President Barack Obama at the White House, he committed his country to a series of ambitious policies aimed at countering the rise in global temperatures.

Xi said China would introduce a national cap-and-trade system in 2017 that would limit carbon emissions across major industrial sectors, from electricity to iron and steel production. He also pledged to match tougher U.S. fuel standards on heavy trucks planned for 2019, and committed $3.1 billion to help poor countries adapt to climate change.

“President Xi has lifted the final political excuse of inaction in Washington,” said Li Shuo, a campaigner for the environmental group Greenpeace.

China’s aid money matches a similar pledge made last year by Obama, though the money has yet to be delivered to the U.N.-backed Green Climate Fund because of Republican refusal to appropriate the funds.

Despite the joint announcement by Xi and Obama, some Republicans remained adamantly opposed to a climate deal.

“If the president was serious about achieving a substantive climate agreement, he would spend more time working with Congress instead of developing press releases with the Chinese government,” said Sen. James Inhofe of Oklahoma. “These public pledges sound good but come with serious economic consequences for the United States.”

Trump has not made any public comments about the agreement and did not immediately respond to an emailed request for comment on Friday.

The pledges mean that the world’s two biggest carbon emitters have now aligned their climate diplomacy going into negotiations for a global accord in Paris this December. It marks a long evolution from the Kyoto climate talks in the 1990s, when China refused to sign any agreement that would limit carbon emissions. That position undermined support for the Kyoto agreement in Congress, which refused to ratify it.

That sentiment remains strong among Republican lawmakers and some Democrats who oppose U.S. measures to limit carbon emissions because, in part, China has been reluctant to do the same. The result has been a standoff between Obama and Congress that hit a nadir in 2010 when the Senate balked at passing the administration’s attempt to enact a national carbon market.

Now Xi says China will move ahead with just such a market.

“The irony is rich. Emissions trading is an American idea; now it’s become an American export,” said David Sandalow, a fellow at Columbia University’s Center on Global Energy Policy and former undersecretary of energy for policy and international affairs.

Other parts of the Chinese package reveal a similar change — in tone, at least.

China’s financial pledge is a “watershed moment” for climate diplomacy, environmental groups say, because it shows a willingness to share the billions of dollars required to help poor countries shift to low-carbon economies and deal with the effects of a hotter planet. China has long seen itself as a developing nation that is expected to be on the receiving end of any international largesse.

Jake Schmidt, international policy director of the Natural Resources Defense Council, said this change in attitude removes a common complaint about China from congressional opponents.

“China is not going to be the recipient of U.S. climate financing, which is how some of our friends on the Hill are painting it,” said Schmidt. “This is a better narrative.”

In fact, Obama is likelier than Xi to be forced to show up in Paris without money. The first $500 million of the president’s $3 billion pledge is held up in thorny budget negotiations on Capitol Hill, where some Republican lawmakers have vowed to block any international climate funding.