UN ambassador Nikki Haley insisted North Korea would get the right message as the international community seeks to halt its arms programme.
Ms Haley said: “It sends the perfect message to North Korea, which is we’re not going to engage in a bad deal.”
She has supported the US President’s move despite it being met with widespread criticism.
The 2015 Iran deal was design to curb the country’s nuclear programme in exchange for a easing of sanctions.
Ms Haley said the US needs to weigh a response to Tehran’s ballistic missile test, foreign arm sales and sponsoring of terrorism.
Earlier the US President stop short of terminating the deal but made it clear the option remained open to him.
Critics have claimed the move will make it harder to forge a similar deal with Kim Jong-un to stop the despot from pursuing more nuclear weapons.
World leaders, including Theresa May, have called on Trump to stay in the multilateral deal.
Mrs May and Angela Merkel both confirmed their support for the deal after a phone call.
A spokeswoman said: “They agreed the UK and Germany both remained firmly committed to the deal.”
“They also agreed the international community needed to continue to come together to push back against Iran’s destabilising regional activity, and to explore ways of addressing concerns about Iran’s ballistic missile programme.”
Insisting the move sends the right message to Pyongyang Ms Haley said: “Should we ever get into a deal, we’re going to hold you accountable. We’re not going to look the other way because we thing we have made a deal and we’re not going to continue to watch it.”
Confirming his decision Trump claimed accused Tehran of “not living up to the spirit” of the agreement and vowed to make sure they never get a nuclear weapon.
Ms Haley said: “What you see is the President is trying to make sure that Iran doesn’t become the next North Korea.”
The UN ambassador said the United States would remain in the deal “right now”.
She said: “I think right now, you’re going to see us stay in the deal, because what our hope is that we can improve the situation, and that’s the goal.”
The President’s decision has left the future of the deal up to the US Congress which now has 60 days to make a decision.