By Hyunsu Yim SEOUL (Reuters) -Russian President Vladimir Putin expressed his willingness to visit Pyongyang soon when he met with North Korean Foreign Minister Choe Son Hui in Russia last week, North Korea’s state news agency KCNA reported on Sunday. Putin also thanked North Korean leader Kim Jong Un for his invitation to visit, KCNA said, citing North Korea’s foreign minister’s assistant office. It would be the Russian leader’s first trip to North Korea in more than two decades. Kremlin spokesman Dmitry Peskov said on Monday that Russia hoped a Putin visit to North Korea, at Kim’s invitation…