HONOLULU -- President Barack Obama has vetoed two measures that would have blocked steps that his administration is taking to address climate change.

One would have nullified carbon pollution standards set by the Environmental Protection Agency. The EPA requires the power sector to slash its carbon output by 32 percent by the year 2030.

The second would have voided a set of national standards designed to reduce the amount of greenhouse gas pollution from existing power plants.

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In a letter notifying Congress of his decision, the president said climate change is a "profound threat" that must be addressed.

"The Clean Power Plan is a tremendously important step in the fight against global climate change," Mr. Obama said in his letter to Republicans.

He added that "because the resolution would overturn the Clean Power Plan, which is critical to protecting against climate change and ensuring the health and well-being of our nation, I cannot support it."

Some Republican lawmakers and presidential candidates scoff at the climate science.

Obama has made addressing climate change a priority. He recently praised a new international climate agreement reached at a Paris conference and credited his administration as being a driving force behind the deal. The president also listed "America's global leadership on climate change" as a top accomplishment of his administration in a Saturday video highlighting the best moments of 2015.

He rejected the measures through a rare "pocket veto," intended to be used when Congress has adjourned, as it did Friday for the year. A pocket vote essentially takes effect when the president fails to sign a bill within 10 days.