TAIPEI, Taiwan — Taiwan’s President Tsai Ing-wen left Saturday for the United States and three South Pacific nations in an effort to crack the diplomatic isolation imposed by rival China.

Tsai will visit the Marshall and Solomon Islands along with Tuvalu while transiting through Hawaii and the U.S. territory of Guam. The three are among just 20 countries that extend Taiwan formal diplomatic recognition.

Tsai’s travels follow Panama’s switching of diplomatic relations to Beijing in June in what was seen as a major diplomatic setback for Taiwan.

“We want to prove to the world that Taiwan is capable of, and is willing to, make more contributions to the international community,” Tsai said Saturday ahead of her departure.

In the Marshalls and Solomons, Tsai will find an “opportunity to better understand the sustainable development needs of the two countries and determine how (Taiwan) can assist in line with steadfast diplomacy,” the government said in a statement posted on its official website.

In Beijing, foreign ministry spokesman Geng Shuang demanded Tsai be barred from transiting through the U.S., which, like most countries, has only unofficial relations with Taiwan.

“Regarding the transit of Taiwan’s leader in the United States, I think her true intention is clear for all to see,” Geng said at a daily news briefing.

Washington should “not allow her to stop over, avoid sending any erroneous messages to the Taiwan independence force, and maintain the general picture of China-U.S. relationship and peace and stability of the Taiwan Strait with concrete efforts,” Geng said. Beijing has lodged “solemn complaints” with the U.S., Geng said.

China claims sovereignty over democratic, self-ruled Taiwan, which split from the mainland amid civil war in 1949, and uses diplomatic and economic pressure to limit the island’s international relations. Washington does not formally recognize Taiwan but maintains close economic, diplomatic and military ties with the island.

While it officially advocates “peaceful unification,” China has never renounced its threat to use force to gain control over Taiwan, which had only distant relations with China for most of its history and was a Japanese colony from 1895 to 1945.

Chinese President Xi Jinping vowed Oct. 18, the first day of a ruling Communist Party congress, that China would not allow anyone to “separate any part of Chinese territory from China,” in a reference to Taiwan.

The vast majority of Taiwanese favor continuing their de facto independent status and Tsai’s top China policymaker told a forum in Taipei Thursday that the two sides needed a “new chapter” in relations and a “new method of interaction.”

“We know that Xi Jinping is an extremely ambitious leader and he doesn’t want to get to 2020 with his Taiwan scorecard a blank,” said Lin Chong-pin, a retired strategic professor from Tamkang University in Taiwan.

He added: “I don’t think Tsai Ing-wen will cross the red line” during her travels, referring to actions and statements that emphasize Taiwan’s formal and legal independence from China.

Beijing resents the Tsai government because her Democratic Progressive Party advocates Taiwan’s formal independence, although Tsai has played down that aim and called for renewed dialogue with China. Beijing cut off exchanges between the two governments last year after Tsai made clear she would not endorse China’s view that Taiwan is a part of China.

Like most Taiwanese allies, the three countries Tsai is visiting are developing nations that look to Taiwan for economic support. Tsai’s entourage has also prepared gifts made by Taiwan aboriginal artisans to play up their ethnic Austronesian links in the South Pacific, the presidential office said.