Taiwan, Foreign Minister Joseph Wu told a U.S. audience on Wednesday, is a “sea fortress” stopping China’s advance into the Pacific and is prepared to share its experience of resisting Beijing’s efforts to undermine it with other democracies.

Although the United States, like other nations, has no official diplomatic connections with Chinese-controlled Taiwan, it is the island’s most major foreign sponsor and weaponry supplier.

Since President Tsai Ing-wen took office in 2016, China has increased military and diplomatic pressure on Taiwan in an attempt to persuade Taipei to recognize Beijing’s sovereignty claims, alarming both Taipei and Washington.

Wu said Taiwan played a “major role” in preserving freedom of passage in the strategically crucial Taiwan Strait and South China Sea, speaking at an online discussion on Taiwan-US ties hosted by the Global Taiwan Institute and attended by many former top US officials.

“Both of them are critical to peace and stability in the Indo Pacific region,” he said. “Most importantly, a democratic Taiwan serves as a sea fortress to block China’s expansionism into the wider Pacific.”

China claims Taiwan as its territory to legitimize its aggression and expansionism, Wu said, adding: “Isn’t this irredentism precisely what gave rise to the Second World War?”

Taiwan faces not only military threats from China, but also cyber attacks, disinformation campaigns and other “grey zone” tactics, he added.

“Taiwan has learned valuable lessons and developed various means to tackle the threat to democracy, and we are more than willing to share this knowledge with fellow democracies.”

There was no immediate response to his comments from China.

Earlier on Wednesday, China’s Taiwan Affairs Office repeated warnings for Taipei’s government not to try and seek formal independence for the island, saying such “wanton provocations and evil acts” would only threaten peace and stability.

China says Taiwan is the most important and sensitive issue in its relations with the United States.

Taiwan says only its people can decide the island’s future.