Mike Pompeo has referred to North Korean leader Kim Jong-un as "Chairman Un" during a diplomatic meeting, ahead of the landmark summit meeting with President Trump.
The secretary of state said the US was starting "to put some outlines around the substance of the agenda for the summit between the President (Donald Trump) and Chairman Un".
What's the issue?
The reference was unusual because in Korea names begin with the family name followed by their given name.
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Kim Jong-un should be referred to as 'Chairman Kim', while Chinese President Xi Jinping would be referred to as 'President Xi'.
The gaffe was revealed in the official transcript released by Pompeo's office after the secretary of state made his second trip to Pyongyang.
Mr Pompeo was mocked on Twitter for following the mistake.
Despite the mistake, Mr Pompeo's trip was deemed a success after the release of three US detainees in North Korea.
President Trump described the release of the three detainees as a "positive gesture of goodwill".
