Despite his promise to withdraw from the Paris Agreement during the campaign, President Trump is "wide open" on whether or not the U.S. should remain in the climate change agreement, Secretary of Defense James Mattis said Saturday.

"We've obviously got a discussion going on about our policy in this regard," Mattis said in an interview on CBS News' "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 afford," the secretary of defense said.

Trump said he would withdraw the U.S. from the Paris Agreement during the campaign. But his advisers are divided on whether or not the U.S. should remain in the pact.

During his trip to the G7 summit this week, the president declined to join the others in the G7 delegation — Canada, France, Germany, Italy, Japan, and the United Kingdom — in reaffirming their commitment to the Paris climate agreement.

Trump tweeted Saturday morning that he would make his "final decision" on the accord next week.

The U.S. signed on to the accord in 2016 under former President Barack Obama.

Though Mattis said he attended discussions in Brussels where climate change was discussed, he said the U.S. position on the issue falls outside his purview.

"Frankly, it's not in my portfolio, that aspect," he said. "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."

The full interview with Mattis will air on CBS on Sunday.