TAIPEI (Reuters) -The mayor of Taipei will visit Shanghai at the end of this month for an annual city forum, his office said on Friday, a trip that will take place against the backdrop of frozen ties between the Taiwanese and Chinese governments. While China has refused to speak to Taiwan's government since President Tsai Ing-wen took office in 2016, believing she is a separatist, city-to-city exchanges had continued until interrupted by the COVID-19 pandemic. Still, Tsai's administration has cautiously been trying to reopen less sensitive people-to-people links since it lifted pandemic-related border controls late last year, aiming to engender goodwill with China, and a group of Shanghai officials made a low-key visit to Taipei in February.