President Barack Obama and Secretary of State John Kerry hailed the newly passed international climate change agreement as a major achievement that could help turn the tide on global warming, but got a quick reminder that Republicans will fight it all the way.
"We've shown that the world has both the will and the ability to take on this challenge," Obama said from the White House.
The immediate reaction of leading Republican critics was a stark reminder of the conflict that lies ahead.
Senate Majority Leader Mitch McConnell of Kentucky said Obama is "making promises he can't keep" and should remember that the agreement "is subject to being shredded in 13 months."