Former President Donald Trump on Sunday boasted his personal ties with North Korean leader Kim Jong-un that he had built during his presidency, stressing America was "safe" then.

Trump made the remarks during a rally in Indianola, Iowa, on the eve of the first vote of the Republican Party's nomination contest in the lead-off state. Hours earlier, Pyongyang fired a suspected intermediate-range ballistic missile into the East Sea in its first missile launch this year.

"Kim Jong-un (is) very smart, very tough, but he liked me and I got along really well with him and we were safe," Trump said during a live-streamed speech.

"They have a massive nuclear stockpile, possibly as big as anybody, and so we did a great job," he added.

During his White House term from 2017-2021, Trump sought direct engagement with Kim, which led to three face-to-face meetings between them, though serious dialogue between the two sides stalled after the no-deal Hanoi summit in February 2019.

On Monday, the Republican Party is set to hold its first vote of the monthslong state-by-state nomination process that will pick its flag-bearer for the November general election.

Polls have shown Trump leading in the race while former South Carolina Gov. Nikki Haley, and Florida Gov. Ron DeSantis are vying for second place.