Addressing the nation on Saturday, U.S. President Barack Obama pledged to continue his efforts to tackle climate change “in the weeks and months ahead.” In his video address, Obama termed global warming “one of the most urgent challenges of our time.”

“When I took office, I said this was something we couldn’t kick down the road any longer – that our children’s future depended on our action. So we got to work, and over the past seven-and-a-half years, we’ve made ambitious investments in clean energy, and ambitious reductions in our carbon emissions,” Obama, whose administration’s flagship effort to reduce emissions from the power sector — the Clean Power Plan — is currently tied up in the courts — said. “We’ve multiplied wind power threefold. We’ve multiplied solar power more than thirtyfold. In parts of America, these clean power sources are finally cheaper than dirtier, conventional power. And carbon pollution from our energy sector is at its lowest level in 25 years, even as we’re continuing to grow our economy.”

The U.S., along with China, is one the biggest emitters of greenhouse gases in the world. Last year, during a key summit in Paris, the U.S. pledged to cut emissions by up to 28 percent below 2005 levels by 2025.

However, the implementation of the Clean Power Plan, which is a key plank in Obama’s efforts to achieve these goals, was, February, stayed by the Supreme Court pending a judicial review. Issued last year, the plan gives the Environmental Protection Agency power to force coal-fired power stations to cut carbon dioxide emissions by about a third by 2030, marking the first nationwide limit on carbon dioxide emission from power generation.

The plan, which required states to submit their emissions reduction plans later this year, faced immediate and fierce opposition from a coalition of Republican states, coal industry and mining groups, who argued that it was an overextension of the president’s executive authority.

Obama’s comments come at a time when the fate of America’s climate pledges is hanging in the balance. Donald Trump — the Republican presidential nominee — has, on several occasions, said he does not believe in anthropogenic climate change, and has also vowed to pull out the Paris agreement if elected.

“We’re not done yet. In the weeks and months ahead, we’ll release a second round of fuel efficiency standards for heavy-duty vehicles. We’ll take steps to meet the goal we set with Canada and Mexico to achieve 50 percent clean power across North America by 2025,” Obama said. “There’s no doubt that America has become a global leader in the fight against climate change. Last year, that leadership helped us bring nearly 200 nations together in Paris around the most ambitious agreement in history to save the one planet we’ve got. That’s not something to tear up – it’s something to build upon.”