BEIJING (AP) — China threatened “resolute countermeasures” over a planned meeting between Taiwan’s president and the United States House speaker during an upcoming trip through Los Angeles.

Diplomatic pressure against Taiwan has ramped up recently, with Beijing poaching Taipei’s dwindling number of diplomatic allies while also sending military fighter jets flying toward the island on a near-daily basis. Earlier this month, Honduras established diplomatic relations with China, leaving Taiwan with only 13 countries that recognize it as a sovereign state.

President Tsai Ing-wen framed the trip as a chance to show Taiwan’s commitment to democratic values on the world stage, as she left Taiwan Wednesday afternoon to begin her 10-day tour of the Americas.

“I want to tell the whole world democratic Taiwan will resolutely safeguard the values of freedom and democracy, and will continue to be a force for good in the world, continuing a cycle of goodness, strengthening the resilience of democracy in the world,” she told reporters before she boarded the plane. “External pressure will not obstruct our resolution to engage with the world.”

Tsai is scheduled to transit through New York on March 30 before heading to Guatemala and Belize. On April 5, she’s expected to stop in Los Angeles on her way back to Taiwan, at which time the meeting with U.S. House Speaker Kevin McCarthy is tentatively scheduled.

The U.S. stops are the most closely watched of her trip.

Spokesperson for the Cabinet’s Taiwan Affairs Office Zhu Fenglian at a news conference Wednesday denounced Tsai’s stopover on her way to diplomatic allies in Central America and demanded that no U.S. officials meet with her.

“We firmly oppose this and will take resolute countermeasures,” Zhu said. The U.S. should “refrain from arranging Tsai Ing-wen’s transit visits and even contact with American officials, and take concrete actions to fulfill its solemn commitment not to support Taiwan independence,” she said.

Speaking later Wednesday, Chinese Foreign Ministry spokesperson Mao Ning said China would “closely follow the development of the situation and resolutely defend national sovereignty and territorial integrity.”

“The United States should stop claiming to set up guardrails for China-U.S. relations while conducting dangerous activities that undermine the political foundation of bilateral ties,” Mao told reporters at a daily briefing.

Transit visits through the United States by Taiwanese presidents have been routine over the years, senior U.S. officials in Washington and Beijing have underscored to their Chinese counterparts.

In such unofficial visits in recent years, Tsai has met with members of Congress and Taiwanese-American civic groups, and has been welcomed by the chairperson of the American Institute in Taiwan, the U.S. government-run nonprofit that carries out unofficial relations with Taiwan.

Tsai transited through the United States six times between 2016 and 2019 before slowing international travel with the coronavirus pandemic. In reaction to those visits, China lashed out rhetorically against the U.S. and Taiwan.

However, the planned meeting with McCarthy has triggered fears of a heavy-handed Chinese reaction amid heightened frictions between Beijing and Washington over U.S. support for Taiwan, trade and human rights issues.

Following a visit by then-House Speaker Nancy Pelosi to Taiwan in 2022, Beijing launched missiles over the area, deployed warships across the median line of the Taiwan Strait and carried out military exercises in a simulated blockade of the island. Beijing also suspended climate talks with the U.S. and restricted military-to-military communication with the Pentagon.

McCarthy, R-Calif., has said he would meet with Tsai when she is in the U.S. and has not ruled out the possibility of traveling to Taiwan in a show of support.

Beijing sees official American contact with Taiwan as encouragement to make the island’s decades-old de facto independence permanent, a step U.S. leaders say they don’t support. Pelosi, D-Calif., was the highest-ranking elected American official to visit the island since then-Speaker Newt Gingrich in 1997. Under the “One China” policy, the U.S. acknowledges Beijing’s view that it has sovereignty over Taiwan, but considers Taiwan’s status as unsettled. Taipei is an important partner for Washington in the Indo-Pacific.

U.S. officials are increasingly worried about China attempting to make good on its long-stated goal of bringing Taiwan under its control by force if necessary. The sides split amid civil war in 1949 and Beijing sees U.S. politicians’ visits as conspiring with Tsai’s pro-independence Democratic Progressive Party to make the separation permanent and stymy China’s rise as a global power.

The 1979 Taiwan Relations Act, which has governed U.S. relations with the island, does not require Washington to step in militarily if China invades but makes it American policy to ensure Taiwan has the resources to defend itself and to prevent any unilateral change of status by Beijing.

Tensions spiked earlier this year when President Joe Biden ordered a Chinese spy balloon shot down after it traversed the continental United States. The Biden administration has also said U.S. intelligence findings show that China is weighing sending arms to Russia for its ongoing war in Ukraine, but has no evidence Beijing has done so yet.

China, however, has provided Russia with an economic lifeline and political support, and President Vladimir Putin and Chinese leader Xi Jinping met in Moscow earlier this month. That was the first face-to-face meeting between the allies since before Russia launched its invasion of Ukraine more than a year ago.

The Biden administration postponed a planned visit to Beijing by Secretary of State Antony Blinken following the balloon controversy but has signaled it would like to get such a visit back on track.

The Foreign Ministry’s Mao said the blame for tensions laid squarely on Washington for boosting relations with Tsai. Beijing has frozen almost all contacts with Tsai’s administration since shortly after she was elected to the first of her two terms in 2016.

“It is not that China overreacts. It is that the U.S. kept emboldening Taiwan independence forces, which is egregious in nature,” she said.

Tsai’s state visits coincide with a 12-day trip to China by her predecessor, Ma Ying-jeou, of the pro-unification Nationalist Party, in an appeal to voters whose descendants arrived with Chiang Kai-shek’s defeated forces in 1949.

Ma has been visiting sites in the former Nationalist capital of Nanjing and emphasizing historical and cultural links between the sides, while avoiding the politically sensitive topics of China’s determination to eliminate Taiwan’s international presence and refusal to recognize its government.

Tsai is barred from seeking a third term and her party is widely expected to nominate Vice President Lai Ching-te to run for the presidency in January.