 Complete the following phrase:  Choe is reportedly a regular participant in track 1.5 and track 2 diplomacy and has experience particularly in the area of North KoreaUnited States relations and nuclear issues. A statement by Choe released before the 2018 North KoreaUnited States Singapore Summit between Donald Trump and Kim Jong-un led to President Trump temporarily canceling the meeting. Choe had referred to US Vice President Mike Pence as a political dummy, angering Trump. Regardless, Choe was a participant in the summit when it took place on 12 June. At the 