Taiwan leader Lai Ching-te's persistent adherence to "Taiwan independence" poses a serious challenge to the one-China principle and peace in the Taiwan Strait, and the Chinese mainland will never tolerate such a stance, a mainland spokesman said on Wednesday.

Since assuming the leadership role in May, Lai has made moves that some say reinforce his "independence" stance, including proposing a continued increase in the island's "defense" budget and referring to the southern Fujian dialect as the Taiwan dialect.

Chen Binhua, a spokesman for the State Council Taiwan Affairs Office, said at a news conference in Beijing that the "Taiwan independence" efforts are disastrous, and the mainland has sufficient capability to thwart any separatist schemes.

In June, the mainland authorities issued guidelines on imposing criminal penalties on staunch supporters of "Taiwan independence" for engaging in or inciting separatist activities, allowing trials in absentia when necessary.

The websites of the Taiwan Affairs Office and the Ministry of Public Security later added a list of 10 "pro-independence" Taiwan politicians who are considered hardliners, and provided ways for the public to provide tips on people demonstrating similar behavior.

"We will carefully verify and identify the tips received, handle them in accordance with the law and regulations, and resolutely crack down on the very small number of stubborn separatists," Chen said.

Despite the complex and severe situation in the Taiwan Strait this year, exchanges and cooperation in various fields between the two sides are still continuing, he added.

In the first half of the year, cross-Strait personnel exchanges increased 99.5 percent year-on-year, according to official data. During the same period, the number of new Taiwan-funded enterprises on the mainland rose 9.2 percent year-on-year, and cross-Strait trade volume increased 7.6 percent.

"This once again proves that no force can change the desire of compatriots on both sides to get closer and develop relations," he added.

The spokesman also called on the United States to handle Taiwan-related affairs properly after Raymond Greene, the new director of the American Institute in Taiwan, said the US will help enhance Taiwan's security and facilitate Lai's "transit" in the US during potential visits to the island's "allies". Greene made the remarks during a news conference in Taipei last week.

Chen said that "the Taiwan leader should not be allowed to 'transit' through the US, and no wrong signals should be sent to 'Taiwan independence' forces".

Sun Yafu, vice-chairman of the Association for Relations Across the Taiwan Straits, said the complex and severe situation in the Taiwan Strait is partly because of increased foreign interference, particularly by the US.

Sun said that since 2017, the US has intensified its efforts to suppress and encircle China, including actions related to Taiwan that have significantly altered China-US relations and have impacted the Taiwan Strait's stability.

Without US support, he said, the DPP authorities in Taiwan would likely be less assertive.

He said that as the US presidential election approaches, Beijing is closely monitoring US policies on China, including economic, trade, technology, financial issues and Taiwan.

Sun criticized the US for not opposing Lai's "two-state" theory, viewing it as a failure to uphold commitments to the one-China policy and non-support for "Taiwan independence".

Warning that such actions negatively affect the peace and stability of China-US relations and the situation in the Taiwan Strait, he said the US should respect China's core interests and uphold the one-China policy.

zhangyi1@chinadaily.com.cn