Taiwan President Tsai Ing-wen pledged on Saturday to deepen security cooperation with Japan to ensure freedom in the Indo-Pacific during a meeting with the ruling Liberal Democratic Party's policy chief.

Although Japan and Taiwan do not have formal diplomatic ties, they have close unofficial relations and both share concerns about China, especially its increased military activities near them.

Meeting in the presidential office in Taipei, Tsai thanked Koichi Hagiuda, the LDP's policy chief, for Japan's support over issues like maintaining security in the sensitive Taiwan Strait.