Following President Donald Trump's pledge to stop U.S. military exercises with South Korea, U.S. Sens. Chris Murphy, D-Conn., and Tammy Duckworth, D-Ill., on Wednesday introduced an amendment to an annual defense policy bill that would require the president to seek input from the defense security before withdrawing U.S. forces from South Korea.

Trump's pledge came after his meeting with North Korean leader Kim Jong Un in Singapore. The president said in an interview with Voice of America on Tuesday that American soldiers on the Korean peninsula "are going to stay. We didn't even discuss that, that wasn't discussed."

"We are going to get out of the war games that cost so much money, because I think number one, it's very provocative, and I want to do it and I think they're very happy about it because it is so provocative. ... and we won't do that as long as we're negotiating in good faith," he added.

The senators' amendment would prohibit Trump from withdrawing U.S. forces from South Korea unless the defense secretary "certifies it is in our national security interest and would not significantly undermine the security of our allies in the region," the joint statement from Murphy and Duckworth says.

"As President Trump's actions cause us to grow more and more isolated in the world, Congress needs to show our allies that the United States won't throw them to the wolves," Murphy said in the statement. ".... I'm freaked out that the president will order troops out of South Korea only for North Korea to, once again, break their word. I'm all for bringing troops home when North Korea no longer poses an existential threat to our friends, but that day is a long time from now — and Congress needs to have a say."