TAIPEI (Reuters) - Taiwan President Tsai Ing-wen has written to Pope Francis to complain about Chinese pressure on the island Beijing claims as its own, saying China seeks to threaten its democracy and freedom.

The Vatican is one of just 15 countries that has diplomatic ties with Taiwan and the only one in Europe. But Taiwan has been concerned by the Vatican's moves to normalize ties with China, especially after a landmark 2018 pact on appointing bishops.

China, which believes Tsai wants formal independence for Taiwan, has heaped pressure on the president, who won re-election by a landslide this month on a platform of standing up to Beijing.

Tsai says Taiwan is an independent country called the Republic of China, its official name.

Taiwan hopes for a peaceful resolution of its differences with China, Tsai wrote in her letter, released by the presidential office on Tuesday, in response to a message from Pope Francis for the World Day of Peace on Jan. 1.

"However, at present dialogue across the Taiwan Strait is filled with difficulties," she wrote.

"The main sticking point is that China has so far been unwilling to let go of its desire to control Taiwan."

She added, "It continues to threaten Taiwan's democratic freedoms and human rights by threatening to use force against Taiwan, fake news, cyber attacks, and diplomatic means."

But despite China's "severe suppression", Taiwan is moving forward, cooperating with friendly and similar-minded countries, so that other democracies recognize it as the best partner for maintaining peace and stability, she added.

China's recent military operations and exercises in the Taiwan Strait and surrounding areas have caused regional unrest and increased international distrust of it, Tsai said.

China has stepped up military activities near Taiwan since Tsai first won office in 2016, flying bomber patrols around the island and sending its latest aircraft carrier, the Shandong, through the sensitive Taiwan Strait in the election run-up.

Beijing cut diplomatic ties with the Vatican in 1951 and remains concerned an independent church in China could threaten its authority.

The 2018 deal, in the making for more than 10 years, gives the Vatican a long-sought say in the choice of bishops in China, previously solely appointed by Communist authorities. Critics, particularly conservative Catholics, have labeled it a sellout.

(Reporting by Ben Blanchard; Editing by Clarence Fernandez)