BEIJING – China on Wednesday condemned Slovenia’s plans to upgrade relations with self-governing Taiwan, which is likely to trigger diplomatic and economic retaliation against the small Central European country.

Chinese Foreign Ministry spokesman Zhao Lijian said China was “shocked by this and strongly opposed to it”, but did not provide immediate details on how Beijing would react.

“This is a dangerous statement by the Slovenian leader, who openly challenges the one-China principle and supports Taiwan’s independence,” Zhao told reporters at a daily briefing, referring to Monday’s comments by Slovenian Prime Minister Janez Jansa.

China argues that Taiwan has its own territory, which should be forcibly placed under its control if necessary, and is stepping up diplomatic pressure on the island to force it into political concessions.

“No one should underestimate the strong determination, strong will and strong ability of the Chinese to defend national sovereignty and territorial integrity,” Zhao said.

Taiwan and China broke up during the 1949 civil war, and the People’s Republic insists it is the island’s sole legal representative, even though it has never ruled it.

Slovenia is following the move of Lithuania, which, contrary to the diplomatic convention, enabled Taiwan to open a representative office in its capital under the name “Taiwan” and not “Chinese Taipei”.

U.S. and Lithuanian officials say China has blocked imports from that northern European country since the Taiwanese government allowed it to open a trade office there called Taiwan.

The U.S. and most other governments, including Lithuania, have diplomatic relations only with Beijing, but maintain commercial and informal political ties with Taiwan’s democratically elected government. Most governments agree to Chinese pressure and require Taiwanese entities to operate under the name Chinese Taipei.

Chinese pressure has reduced the number of official Taiwanese diplomatic allies to just 14.

Beijing retaliated for Lithuania’s move by expelling the Lithuanian ambassador, and Lithuania has since closed its embassy in Beijing.

Taiwan has responded by setting up a $ 1 billion loan program to finance projects by Lithuanian and Taiwanese companies, and by setting up a $ 200 million investment fund to help the Lithuanian economy.

Both Lithuania and Slovenia are members of the European Union, which is increasingly strongly opposed to Beijing’s aggressive political and economic moves. Both are also members of NATO and intend to establish their offices in Taiwan, a close ally of the United States.

In his comments, Jansa said that ties with Taiwan would not include an exchange of ambassadors, but would be at the same level as many EU countries maintain with the island.

Regarding Lithuania, he said it was “scary” how China was trying to isolate small European nations, saying it would harm Beijing’s interests in the long run.

In Taipei, Foreign Ministry spokeswoman Joanne Ou praised Jansa on Tuesday as a “long-time friend of Taiwan” who had visited him several times.

“We would like to respond positively to the establishment of representative offices, express a high degree of welcome and sincere thanks,” Ou told reporters.