China severed diplomatic ties with Lithuania on Sunday, expressing deep dissatisfaction with the Baltic state after Taiwan established a de facto embassy there, escalating a row that has engulfed Washington.

China regards self-ruled and democratically governed Taiwan as its territory, with no right to the trappings of a state, and has increased pressure on countries to downgrade or sever relations with the island, even if they are not official.

Lithuania expressed regret over China’s move, but defended its right to expand cooperation with Taiwan while adhering to Beijing’s “One China” policy, and announced that its foreign minister would travel to Washington to discuss trade and investment projects.

Meanwhile, Taiwan reported that two Chinese nuclear-capable H-6 bombers flew to the island’s south on Sunday, part of a pattern of what Taipei sees as military harassment designed to put pressure on the government.

Beijing had previously expressed its displeasure with Lithuania, which has formal relations with China but not Taiwan, for allowing the island to open an office in the country under the name Taiwan. In August, China recalled its ambassador.

Other Taiwan offices in Europe and the United States refer to the city of Taipei rather than the island itself. The Taiwanese Representative Office in Lithuania, on the other hand, finally opened on Thursday.

In a blunt statement, China’s Foreign Ministry stated that Lithuania had disregarded China’s “solemn stance” and basic international relations norms.

Relations would be downgraded to the level of charge d’affaires, one rung below ambassador, according to Beijing.

The move “undermined China’s sovereignty and territorial integrity, as well as grossly interfered in China’s internal affairs,” it said, setting a “bad precedent internationally.”

“We urge the Lithuanian side to immediately correct its mistakes and not underestimate the Chinese people’s firm determination and staunch resolve to defend national sovereignty and territorial integrity,” China’s foreign ministry said.

No matter what Taiwan does, it cannot change the fact that it is part of China, it said.

WASHINGTON VISIT

Lithuanian Prime Minister Ingrida Simonyte said on Sunday that the establishment of the non-diplomatic representative office should not have come as a surprise to anyone.

“According to our government’s plan, Lithuania wants a more intense economic, cultural, and scientific relationship with Taiwan,” she explained. “I want to emphasize that this step does not imply any disagreement or conflict with the ‘One China’ policy.”

On Sunday, the prime minister of Lithuania’s larger EU neighbor Poland stated his support for Vilnius’ stance.

Taiwan asserts that it is an independent country known as the Republic of China, and that the People’s Republic of China has never ruled it and has no right to speak for it.

Taiwan’s Mainland Affairs Council slammed China’s “rudeness and arrogance,” claiming that Beijing had no right to comment on a matter that was not an internal Chinese matter and was solely between Taiwan and Lithuania.

Taiwan has been encouraged by growing international support in the face of China’s military and diplomatic pressure, particularly from the US and some of its allies.

Washington rejects attempts by other countries to meddle in Lithuania’s relationship with Taiwan, according to U.S. Under Secretary of State Uzra Zeya.