Donald Trump is set to announce Thursday at 3 p.m. whether the U.S. will stay in the Paris Agreement climate framework.

White House officials have signalled withdrawal was likely to reporters, but Trump has been known to change his mind at the last minute on such major decisions, as happened recently with the NAFTA trade deal.

Abandoning the pact was one of Trump’s principal campaign pledges, but America’s allies have expressed alarm about the likely consequences. Top White House aides have been divided, and Trump’s decision may not be entirely clear cut. Aides have been deliberating on “caveats in the language,” one official said.

The Paris Agreement was struck in 2015 and months later the U.S. and China jointly said they would sign off on the deal. The agreement went into effect for the U.S. in November 2016.

Jean-Claude Juncker, president of the European Commission, has criticized Trump’s resistance to the deal, saying the U.S. president doesn’t understand the fine print of the agreement and that the process of formally withdrawing could take two to three years.

Canada has said its participation in the deal is ironclad regardless of the position the U.S. takes.

You can watch the announcement here at 3 p.m. ET.