President Barack Obama said Sunday he doesn’t “know what he means” when he talks about President Donald Trump’s decision to withdraw from the Paris climate agreement, calling it “a serious mistake.”

In a nationally televised address, Obama said Trump’s withdrawal from the deal “is not only reckless and dangerous, it is not a decision that I can accept.”

“There is a difference between saying that you are withdrawing from a deal that you believe in and saying that your policies will make it more difficult to do what we believe in,” he said.

“There are serious consequences for making decisions like that.

The United States of America is not the world’s policeman.”

Trump signed an executive order withdrawing from the climate accord, which the U.S. has signed on behalf of nearly 200 countries around the world.

The move followed months of pressure from environmental groups and other groups to end the deal, and is the most significant change in decades.

Trump has said the move will “make it more expensive and difficult to operate in the world.”

He also has questioned the wisdom of the Paris accord, saying he would have preferred the deal not been adopted.

The president said the Paris agreement was reached under “tough conditions” and would “leave the world safer and more prosperous.”

“This decision will affect our business, our livelihoods, our businesses, and our businesses depend on the prosperity of the United States,” he added.

Obama has been a strong supporter of the deal and was among the first U.N. leaders to attend the signing ceremony in December.

“We have to do everything we can to make sure that we are on the right side of history,” Obama said in his speech.

He also said he would be seeking Congressional approval to exit the accord, something that hasn’t happened since 1997, when the Bush administration pulled out of the agreement.

“It’s important to understand that the United Nations is a world body,” he continued.

“So as a global community, it can’t decide on every decision that’s made by each individual nation.

But we have to be able to say, well, you know, this is the decision that we’re going to make.”

Obama said he will continue to pursue a “constructive” approach to the climate agreement.

But he said the United Kingdom, France and other nations have been “trying to do something that is a little bit different.”

“I’m going to be working with them, I’m going, I know they’re working on this,” Obama told CBS’ Face the Nation.

“But I will be seeking Congress’ approval to do that.

I will not do it unless Congress does the right thing.”

Obama also defended his administration’s actions in dealing with the Zika virus outbreak.

“I think we’ve been doing a lot of things that are not only working, but that are making a difference,” he told CBS News’ John Dickerson.

“When we say we’re taking on a lot, we are.”

In an interview Sunday on NBC’s Meet the Press, former President Bill Clinton also said the Trump administration’s decision “is the most dangerous thing I’ve ever seen in my lifetime.”

“It is the biggest mistake of the modern presidency,” Clinton said.