The United States House Speaker Nancy Pelosi on Wednesday said that she and other members of Congress in a visiting delegation are showing they will not abandon their commitment to Taiwan, a self-governing island.

In a short speech during a meeting with Taiwanese President Tsai Ing-wen, the US House Speaker said, “Today the world faces a choice between democracy and autocracy. America’s determination to preserve democracy, here in Taiwan and around the world, remains ironclad.”

Also read: How China is punishing Taiwan for US House Speaker Nancy Pelosi’s visit

China, which has been claiming that the self-governing island as its territory and opposes any engagement by Taiwanese officials with foreign governments, announced multiple military exercises around the island, parts of which will enter Taiwanese waters, and issued a series of harsh statements after the delegation touched down Tuesday night in the Taiwanese capital, Taipei.

“Such an act equals sealing off Taiwan by air and sea, such an act covers our country’s territory and territorial waters, and severely violates our country’s territorial sovereignty,” Capt. Jian-chang Yu said at a briefing by the National Defense Ministry.

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According to Chinese state media, the military exercises, including live fire, are to start from Thursday. It is also reported that the upcoming “military operations” will be the largest aimed at Taiwan since 1995, when China fired missiles in a large-scale exercise to show its displeasure at a visit by then-Taiwanese President Lee Teng-hui to the United States.

On Tuesday night, China’s official Xinhua News Agency announced the military actions, along with a map outlining six different areas around Taiwan. Arthur Zhin-Sheng Wang, a defence studies expert at Taiwan’s Central Police University, said three of the areas infringe on Taiwanese waters, meaning they are within 12 nautical miles (22 kilometres) of shore.

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Using live fire in a country’s territorial airspace or waters is risky, said Wang, adding that “according to international rules of engagement, this can possibly be seen as an act of war.”

Pelosi’s trip has heightened US-China tensions more than visits by other members of Congress because of her high-level position as leader of the House of Representatives. She is the first speaker of the House to visit Taiwan in 25 years, since Newt Gingrich in 1997.

Also read: 21 Chinese military planes enter Taiwan’s airspace ahead of Pelosi’s visit

On Wednesday, Taiwanese President Tsai responded to Beijing’s military intimidation.

“Facing deliberately heightened military threats, Taiwan will not back down,” Tsai said at her meeting with Pelosi. “We will firmly uphold our nation’s sovereignty and continue to hold the line of defence for democracy.”

Shortly after Pelosi landed Tuesday night, China announced live-fire drills that reportedly started that night, as well as the four-day exercises starting Thursday.

Also read: China to conduct missile, military drills around Taiwan after Nancy Pelosi’s visit

The People’s Liberation Army Air Force also flew a contingent of 21 war planes Tuesday night, including fighter jets, toward Taiwan. Chinese Vice Foreign Minister Xie Feng also summoned the US ambassador in Beijing, Nicholas Burns, to convey the country’s protests the same night.