On June 12, 2018, Trump and North Korean dictator Kim Jong-un held a historic summit meeting in Singapore. They signed a joint statement in which North Korea agreed to begin denuclearizing in exchange for security assurances. When asked about whether he believed North Korea could be trusted, and what he would do if they backed out of any the agreement, Trump replied,

I may be wrong, I mean I may stand before you in six months and say, ‘Hey I was wrong.’ I don’t know that I’ll ever admit that, but I’ll find some kind of an excuse.

Trump had said he didn’t need to prepare or take notes for the historic meeting.

Following the summit, Trump declared an end to joint defensive exercises in South Korea. North Korea has not yet denuclearized. Congress passed budget legislation prohibiting the reduction of US forces in South Korea below 22,000.

The Hill – Trump: If I was wrong about Kim, ‘I’ll find some kind of an excuse’
Business Insider – Trump says if he ends up being wrong about Kim Jong Un, he probably won’t admit it and will find ‘some kind of an excuse’
The Hill – Bipartisan House group introduces bills to stall Syria, South Korea troop withdrawals
WIkipedia – 2018 North Korea–United States Singapore Summit