BEIJING (Reuters) - China s former ambassador to the United Nations has taken up a new role as a deputy head of the country s Taiwan policy-making body, the Taiwan Affairs Office, part of a leadership reshuffle connected to a key Communist Party Congress opening next week. Taiwan is one of China s most important and sensitive issues. China considers proudly democratic Taiwan to be a wayward province and has never renounced the possibility of using force to bring the island under its control. Veteran diplomat Liu Jieyi served as China s ambassador to the United Nations from August 2013 until last month when he was recalled to Beijing to await a new role. Liu has now taken up the position as the top ranked of four deputy heads of the Taiwan Affairs Office, according to an updated list of the office s leadership positions posted on its website. Chinese media reported on the change on Wednesday. While China considers Taiwan to be an internal affair it is not unusual for Chinese diplomats to serve in the Taiwan Affairs Office. Zhang Zhijun remains head of the Taiwan Affairs Office, a position he took in 2013 replacing Wang Yi, who currently serves as China s foreign minister. Zhang also previously worked for the foreign ministry. As the top ranked deputy at the office, Liu stands in line to take over from Zhang if he also assumes another position in the next few months.  The once-every-five-years party Congress will see many people take up new posts between now and the annual meeting of parliament in March. Taipei s relations with Beijing have deteriorated sharply since President Tsai Ing-wen, leader of the pro-independence Democratic Progressive Party, took office last year. China suspects she wants to push for the island s formal independence, a red line for Beijing. China has cut off a regular dialogue mechanism with Taiwan, ramped up military drills around the island and stepped up international pressure to limit Taiwan s diplomatic footprint. Tsai, who has pledged to maintain peace with China, said this week her government was still seeking breakthroughs in ties with Beijing and promised consistent and stable policies.[nL4N1ML1L8] 