President Obama and Chinese President Xi Jinpeng have announced aggressive new goals for cutting or capping carbon dioxide emissions over the next 10 to 15 years.

But a battle is looming with congressional Republicans over Obama’s part of the plan—that is, sharper U.S. CO2 reductions.

Under an agreement which Obama and Xi announced on Nov. 11 in Beijing, the U.S. will aim to trim its net greenhouse-gas emissions 26% to 28% below their 2005 levels by 2025.

That amounts to a doubling of the pace of average annual carbon emissions cuts, to between 2.3% and 2.8% from 1.2% now, according to the White House.

Obama said the plan "puts us on a path to achieving the deep emissions reductions by advanced economies that the scientific community says is necessary to prevent the most catatstrophic effects of climate change."

For its part, China has agreed to “peak” its CO2 emissions before 2030, the first time the country has pledged to set such a limit.

To help reach the target, China will increase the share of its energy consumption from fossil-fuel sources to about 20% by 2030. The White House said that would mean adding 800 GW to 1,000 GW of power from nuclear, wind, solar and other non-fossil sources.

Together, the two countries produce more than a third of global greenhouse-gas emissions, the White House said.

Xi said in a joint Nov. 12 press conference with Obama that the two leaders also had "agreed to make sure that international climate-change negotiations will reach an agreement as scheduled at the Paris conference in 2015."

Obama called the climate agreement "a major milestone in the U.S.-China relationship."

But top congressional Republicans blasted Obama’s announcement and warned they will fight the plan in the new Congress, which convenes in January.

In the Nov. 4 elections, the GOP won control of the Senate, starting in 2015, and increased its House majority. GOP leaders said they would aim to ease, in particular, Environmental Protection Agency regulations.

Senate Minority Leader Mitch McConnell said in a Nov. 12 statement, “This unrealistic plan, [which] the president would dump on his successor, would ensure higher utility rates and far fewer jobs.”

House Speaker John Boehner (R-Ohio) called Obama’s announcement “another sign that the president intends to double down on his job-crushing policies no matter how devastating the impact for America’s heartland and the country as a whole.”

Obama’s plan did win praise from other quarters. Senate Majority Leader Harry Reid (D-Nev.) said the two countries’ joint announcement “is exactly what is needed to ensure that America’s efforts to clean up our energy supply are replicated around the world.”

Sierra Club President Michael Brune said China’s new 20% non-fossil energy goal is “a huge step forward that signals a historic shift away from dirty fossil fuels and could drive a new global competition for clean-energy technology.”

The White House noted several initiatives to reduce greenhouse gases, including a proposed EPA rule to cut powerplant emissions and Obama’s directive to the EPA and Dept. of Transportation to issue, by March 2016, tighter fuel-efficiency standards for medium- and heavy-duty vehicles.

The joint U.S.-China announcement also included initiatives to expand cooperative efforts in clean-energy research and development, carbon capture and storage, and a new “climate-smart, low-carbon cities initiative.”