Taiwan's President Ma Ying-jeou was due to leave for the Vatican last night to attend the inauguration mass of Pope Francis in a move that may stoke tensions with the mainland.
The Vatican is one of the 23 states that recognise Taipei instead of Beijing as representing China, and is Taiwan's only diplomatic ally in Europe. Beijing still refuses to renounce the use of force against the island in its long-stated goal of re-taking Taiwan, which has ruled itself since the end of a civil war in 1949.
Although cross-strait ties have warmed in recent years, the mainland opposes any steps that imply recognition of Taiwan by other countries, including their hosting visits by senior government leaders from the island.
The Vatican has said it would welcome Ma joining other foreign dignitaries who will attend the installation of Pope Francis tomorrow, adding that it would "receive him with every honour".
"I really look forward to this visit ... I'd like to extend Taiwanese people's sincere gratitude and well-wishes to the Vatican," Ma wrote in a Facebook message.
Beijing's foreign ministry spokeswoman Hua Chunying called on Taiwan to "bear in mind the overall situation and deal prudently with sensitive issues" at a regular press briefing.
"We hope that the Vatican will take concrete steps to create conditions for the improvement of China-Vatican relations and gradually remove barriers."
Hua called on the Vatican to sever its diplomatic ties with Taiwan and to "recognise the Chinese government as the sole legal representative of all China".
China broke ties with the Vatican in 1951 and six years later set up its own church that does not recognise the pope.