WASHINGTON — President Barack Obama ordered the federal government Thursday to cut its greenhouse gas emissions by nearly half over the next decade, driving his climate change agenda forward despite percolating challenges from Republicans.

By curtailing pollution within the U.S. government, Obama sought to increase political pressure on other nations to deal seriously with climate change. The U.S. and other nations will soon announce how much they’re willing to cut their national emissions as part of a global climate treaty to be finalized in December; scientists warn if those pledges are too lax, the treaty could be too weak to stop the worst effects of global warming.

“We thought it was important for us to lead by example,” Obama said. “These are ambitious goals, but we know they’re achievable goals.”