Taiwanese human rights activists on Nov. 7 call on President Trump to ask for the release of Lee Ming-che, who was charged with political crimes in China. (Chiang Ying-Ying/AP)

President Trump's visit to Beijing has been watched closely around the world — but few countries have had more reason to scrutinize it than Taiwan.

Though Taiwan was not expected be a major focus of his talks with China's president, some here worried the "issue" would come up during discussions of North Korea's weapons program or trade.

The fear is some kind of swap involving U.S. support for Taiwan and Chinese ties with North Korea could be under discussion and Taiwan would become "a bargaining chip," in the words of Katherine Chang, the minister for mainland affairs.

Trump and Chinese President Xi Jinping did not mention Taiwan in their public statement after meeting on Thursday. The pair also did not take questions from reporters. When a Taiwanese reporter attempted to ask Secretary of State Rex Tillerson about the issue after a news briefing, he did not respond.

China's Foreign Ministry later, however, released a statement that said Xi had reiterated the importance of Taiwan to Beijing during his meeting with Trump. "The Taiwan issue is the most important and sensitive core issue in the Sino-U. S. relations, and it is also the political foundation for the Sino-U. S. relations," he said, according to the statement.

Xi also asked the United States to continue to abide by the one-China policy, which rules out diplomatic recognition for Taiwan.

The statement will cause concern in Taiwan. "It'd be better if Taiwan was not mentioned at all," Szu-chien Hsu, the chairman of the government-funded Taiwan Foundation for Democracy, had said before the presidents met.

Taipei has long worried about Beijing raising the one-China issue during its meetings with the United States, according to Bonnie Glaser, a senior fellow at the Center for Strategic and International Studies. Under the Trump administration there have been more concerns because of the "unpredictable president who in the past has said some extreme things about Taiwan," she said.

Shortly after Trump's election last year, there had been hopes for stronger U.S.-Taiwan ties. On the campaign trail Trump had frequently been critical of China, and a number of close advisers held sympathetic views of Taiwan's concerns. In early December, Trump received an unprecedented congratulatory phone call from Taiwan's president, Tsai Ing-wen.

The call seemed to signal a change. Though the United States does not diplomatically recognize Taiwan, it enjoys a strong informal relationship with the country and is bound to protect it by law.

At first Trump defended the call and suggested his administration's position on the one-China policy would depend on whether he could "make a deal" with China on trade and other issues.

Later, though, he said he would not speak to the Taiwanese president again without checking with China first.

Analysts in Taiwan have been paying close attention to Trump's interactions with veteran foreign policy expert Henry Kissinger, with some suggesting Kissinger is advocating Trump make a major agreement on U.S.-China relations with Beijing.

Hsu, of the Taiwan Foundation, said this was "just a rumor," but added there were real concerns about what lies behind Trump's decision-making. "He is known for his transactional style of policymaking."

The Trump Administration has repeatedly said it views Chinese economic and diplomatic pressure as vital for persuading North Korea to abandon its nuclear weapons program.

During a news conference in South Korea on Tuesday, the president suggested Xi had been "very helpful" on the North Korea issue and China was "trying very hard to solve the problem."

Other factors add further uncertainty to the relationship. Trump has made clear repeatedly trade imbalances are key points of tension with foreign allies: The United States has logged an average trade deficit of $5.4 billion with Taiwan over the past five years.

One way to address that would be for Taiwan to boost its defense spending, which is considered low by U.S. officials. It stands at around 2 percent of gross domestic product and lags far behind that of China, its primary geopolitical rival. "Taiwan must do better," James Moriarty, chairman of the American Institute of Taiwan, said of the country's defense spending during an event last month at Brookings.

Still, diplomats have stressed any significant change in U.S. policy on Taiwan is unlikely, noting an arms sale of $1.42 billion agreed upon this summer.

At the same time, Taipei is pursuing a number of policies that seem designed to curry favor with the Trump administration, including modest defense spending increases, a proposed bilateral trade agreement and a ban on all trade with North Korea.

Foreign Minister David Lee told reporters this week Taiwan had also been attempting to use its close relationship with Japanese Prime Minister Shinzo Abe to influence Trump's policy.

Trump is not the only wild card. Speaking at a Foreign Ministry luncheon on Tuesday, Alexander Huang, chairman of Taiwan's Council on Strategic and Wargaming Studies, said whether Taiwan ends up a bargaining chip will also come down to Xi, who is in a powerful position after China's recent party Congress.

"Many have debated here in Taiwan whether President Trump will trade Taiwan in exchange for China's position in North Korea," Huang said. "But my hunch is that even if President Trump makes such an offer, President Xi would say no: 'Taiwan is not in your hands. It's in mine.'"

David Nakamura and Luna Lin in Beijing contributed to this report.