TAIPEI, Taiwan (AP) — The three candidates running in next month’s Taiwanese presidential election will hold a televised debate on Dec. 30 as the race heats up under pressure from China.

The outcome of the Jan. 13 election could have a major effect on relations between China and the United States, which is bound by its own laws to provide Taiwan with the weapons it needs to defend itself and to regard threats to the self-governing island as a matter of “grave concern.”

Differences over Taiwan, which China claims as its own territory, are a major flashpoint in U.S.-China relations.

The debate will feature current Vice President William Lai of the Democratic Progressive Party; Hou Yu-ih, a local government leader representing the main opposition Nationalist Party, or KMT; and former Taipei mayor Ko Wen-je, of the smaller Taiwan People’s Party.

Lai, whose party favors the status quo of de-facto independence, is favored to win the election, ensuring that tensions with China will likely remain high. The KMT, which formerly ruled in China before being driven to Taiwan amid the Communist takeover of the mainland in 1949, formally backs political unification between the sides, a prospect most Taiwanese reject. Ko, who briefly flirted with an alliance with the KMT, has advocated restarting talks with China.

“The whole world wants to know whether the people of Taiwan will continue to move forward on the path of democracy in this major election, or whether they will choose to rely on China, follow a pro-China path, and lock Taiwan into China again,” Lai said in a recent speech.

Since the end of martial law in 1987, Taiwanese politics has been deeply embedded in community organizations, temples, churches and other networks that mobilize voters to bring their enthusiasm to rallies and come out to choose candidates, who mostly focus on local issues.

Beijing has sought to isolate Taiwan’s government, demands political concessions for talks and threatens to annex the island by force. It has worked to gain influence with the island’s vibrant media, spread disinformation, exerted economic pressure by barring some Taiwanese products and offered incentives on the mainland for companies and politicians it considers friendly.

Meanwhile, it has used its clout to keep Taiwan out of most international gatherings and organizations and has been gradually poaching the island’s remaining handful of diplomatic allies.

On the military front, it has fired missiles and regularly sends warplanes and navy ships near the coast, though still outside Taiwanese waters and airspace.

On Friday, Taiwan’s Defense Ministry said it spotted a Chinese surveillance balloon in the Taiwan Strait along with a large-scale movement of military aircraft and ships.

A Chinese Foreign Ministry spokesperson Tuesday warned that Taiwan’s independence is “as incompatible with cross-Strait peace as fire with water, which means war and leads to a dead end.”

A debate among the vice presidential candidates is scheduled for Jan. 1.