Here's What You Need to Know About President Obama's Decision to Reject the Keystone XL Pipeline

In the year’s biggest victory for environmentalists, President Barack Obama announced Friday that he will reject an application from Canadian company TransCanada to construct the Keystone XL pipeline.

The pipeline, which would allow crude oil from Canada’s oil sands to reach ports and refineries in the US, has been a major controversy for Obama ever since he took office. The White House spent years deliberating on the issue. During that time, environmental groups accused Obama of not backing up his rhetoric on climate change with real action, and Republicans in Congress accused him of blocking a job-creating infrastructure project.

In his announcement today, the president said the State Department’s analysis had shown the pipeline would not significantly benefit the US economy.

"The State Department has decided that the Keystone XL pipeline would not serve the national interests of the United States. I agree with that decision," Obama said.

The timing of the announcement is significant, as it comes just weeks before the beginning of major international climate negotiations in Paris. Obama’s decision will "reverberate" with other countries and sends a strong message that the United States is serious about taking action to stop climate change, said Jennifer Morgan, director of the global climate program at the World Resources Institute.

Obama said that pipeline had been given an "overinflated role in the political discourse" by both its supporters and detractors. Still, he framed his decision as a key element of his climate legacy.

"America is now a global leader when it comes to taking serious action to fight climate change," he said. "Today we continue to lead by example."

Watch the full speech below:

This post has been updated.