Chinese president Xi Jinping met the leader of Taiwan's opposition party Tuesday as Beijing's relations with the island's new president worsen.

Xi met Kuomintang (KMT) leader Hung Hsiu-chu at the Great Hall of the People, the official Xinhua news agency said.

He called on Taiwan to respect the "One China principle" and stressed the importance of protecting "national integrity".

Cross-strait ties have deteriorated under Taiwan's first female president Tsai Ing-wen, whose China-sceptic Democratic Progressive Party took office in May after its landslide victory over the KMT.

Tsai has refused publicly to accept the concept of "One China", prompting Beijing to cut off all official communication with her government.

Beijing sees Taiwan, which has ruled itself since KMT forces fled there at the end of the civil war in 1949, as part of its territory requiring reunification.

Xinhua previously reported that Hung was leading a delegation from Taiwan to "promote stability and peace across the Taiwan Strait".

On Monday the group stopped in Nanjing to visit the mausoleum of Chinese revolutionary Sun Yat-sen before the 150th anniversary of his birth.

Hung -- whose stance leans towards China and who is also her party's first female leader -- was chosen to lead it in March despite being ousted as the KMT's presidential candidate last October due to her conservative views.

At the time Xi sent Hung a congratulatory note in which he warned against any pro-independence movement on the island.