The situation in the Taiwan Strait is "complex and grim", Chinese President Xi Jinping wrote in a congratulatory letter on Sunday to the newly elected leader of Taiwan's main opposition party, who has pledged to renew talks with Beijing.

Taiwan's Kuomintang (KMT) elected as their leader on Saturday former New Taipei City mayor Eric Chu, who said he would rekindle stalled high-level contacts with China's ruling Communist Party.

China claims Taiwan as its own territory and has stepped up military...