President Trump has made his decision to withdraw from the Paris climate accord, according to two sources with direct knowledge of the decision. Details on how the withdrawal will be executed are being worked out by a small team including EPA Administrator Scott Pruitt. They're deciding on whether to initiate a full, formal withdrawal — which could take 3 years — or exit the underlying United Nations climate change treaty, which would be faster but more extreme.

Why this matters: Pulling out of Paris is the biggest thing Trump could do to unravel Obama's climate legacy. It sends a combative signal to the rest of the world that America doesn't prioritize climate change and threatens to unravel the ambition of the entire deal.

The other outliers: The only other two countries that aren't supporting the deal are Nicaragua and Syria.

How it happened: A letter from 22 Republican Senators (including Mitch McConnell) that called for a clean exit had reinforced Trump's instincts to withdraw, and the president had been telling confidants over the past week that he was going to pull out.

Trump's last comment on the issue, sent this morning on Twitter: "I will be announcing my decision on the Paris Accord over the next few days. MAKE AMERICA GREAT AGAIN!"

Read next: Why Trump is pulling out of the Paris deal.