By Rebecca Morin

May 27, 2017 - President Donald Trump is "wide open" on the Paris climate accord as "he takes in the pros and cons," Secretary of Defense Jim Mattis said in an interview to air Sunday.

"We've obviously got a discussion going on about our policy in this regard," he said on CBS' "Face the Nation." "I was sitting in on some of the discussions in Brussels, by the way, where climate change came up, and the president was open. He was curious about why others were in the position they were in – his counterparts in other nations – and I'm quite certain the president is wide open on this issue as he takes in the pros and cons of that accord."

Trump on Saturday wrote on Twitter that he would make his final decision next week on whether the U.S. would remain in the climate accord, an international agreement to curb carbon emissions. Throughout the campaign, Trump had pledged to withdraw from the pact.

Mattis, however, said the U.S. position on climate change is "not inside my portfolio."

"Obviously we deal with the aspects of a warming climate in the Department of Defense, and to us, that's just another one of many factors we deal with which we call the physical environment," he continued.

During the interview, Mattis also said Trump's message on NATO is "a consistent message" that the U.S. has given allied nations in the past.

During remarks at NATO's headquarters in Brussels, Trump criticized "23 of the 28 member nations" for not paying enough for their national defense.

"Having been a NATO officer, under President Bush and President Obama, and then having been back there in Brussels representing the Department of Defense under President Trump … this is a consistent message that we have given the NATO nations," Mattis said.

"They get the best defense in the world, the NATO countries, and we've all got to be willing to deal with it like a bank: if you want to take something out of it you've got to put something into it.

"And the bottom line is that nations are spending more on defense now than they were five years ago or ten years ago," he said.