Recent interactions between Lai Ching-te, the leader of China's Taiwan region, and U.S. officials, and his "stopover" in the U.S. have sparked strong opposition from the Chinese mainland, which reiterated its adherence to the one-China principle and warned the U.S. against crossing China's "red line."

It is reported that Lai has embarked on a tour of Taiwan region's so-called "diplomatic allies" in the Pacific, making a two-night stopover in Hawaii followed by a one-night stop in Guam, a U.S. territory. During his stay in the U.S. state of Hawaii, he reportedly held a phone call with former U.S. House Speaker Nancy Pelosi.

The Chinese Foreign Ministry on Monday firmly condemned any form of official interaction between the U.S. and Taiwan region, and urged Washington to cease supporting Taiwan secessionists.

"The Taiwan question is at the core of China's core interests, and the first red line that cannot be crossed in China-U.S. relations," Lin Jian, a spokesperson for the Foreign Ministry said.

He urged the U.S. to fully see the separatist nature of Lai Ching-te and the Democratic Progressive Party authorities, fully understand the grave damage of Taiwan secession activities to peace and stability in the Taiwan Straits, fully abide by the one-China principle, and stop meddling in affairs related to Taiwan, which are China's internal affairs.

What exactly is the one-China principle? And why is the one-China principle so important? Here are some facts you should know.

UNGA Resolution 2758

The United Nations General Assembly adopted Resolution 2758 in October 1971, which expelled the representatives of the Taiwan authorities and restored the seat and all the lawful rights of the government of the People's Republic of China (PRC) at the UN, marking a historic milestone for China's diplomacy.

The resolution clearly states that "the United Nations considers 'Taiwan' as a province of China with no separate status," and the "'authorities' in 'Taipei' are not considered to... enjoy any form of government status." At the UN, the island is referred to as "Taiwan, Province of China."

In multiple legal papers issued by the UN Office of Legal Affairs, the international organization clearly stated that "Taiwan has no independent status as a province of China," "the Taiwan authorities do not enjoy any form of government status," and that the correct titles for Taiwan should be "Taiwan Province of China," "Taiwan, China," or "Chinese Taipei." These documents affirm that there is only one China and Taiwan is part of China.

To date, 183 countries have established diplomatic relations with the PRC on the basis of the one-China principle.

The 1992 Consensus and one-China principle

In October 1992, the mainland-based Association for Relations Across the Taiwan Straits and the Taiwan-based Straits Exchange Foundation held talks in Hong Kong. Following these talks and a series of subsequent correspondence and telephone exchanges that year, the two organizations agreed to state that "the two sides of the Taiwan Straits both stick to the one-China principle."

There are documents and written records setting out the process of reaching the 1992 Consensus and its content. Its essence lies in the affirmation that "both sides of the Taiwan Straits belong to one China and will work together towards national reunification," which defines the nature of cross-Straits relations and lays the political foundation for the development of ties across the Straits.

Since then, the two sides have set aside their differences and initiated exchanges and dialogues. In 2001, the Taiwan authorities permitted direct ferry travel between the Chinese mainland's Fujian Province and the islands of Kinmen and Matsu, ending decades of isolation for the islands from the mainland. Seven years later, direct two-way mail, transport and trade across the Straits were fully established between the two sides, significantly facilitating the flow of people, goods and capital.

However, the Democratic Progressive Party authorities have refused to recognize the 1992 Consensus that embodies the one-China principle since 2016, a stance that has been denounced by the State Council Taiwan Affairs Office for "disrupting the foundation of peaceful development of cross-Straits relations."