China called Taiwan’s vice president a “troublemaker” whose views risk sparking a conflict, a sign that Lai Ching-te will likely have testy relations with Beijing if he becomes the island’s next leader.

Lai used a recent stop in the US to encourage “separatism,” Beijing’s Taiwan Affairs Office said in a statement late Tuesday. It called a recent pledge Lai made in an interview with Bloomberg Businessweek that he would maintain peace in the Taiwan Strait “a complete lie.”

“Such a person will only bring risks of fierce war,” the office that handles Beijing’s relations with Taipei said.

China Says Taiwan’s VP Lai Brings Risk of War (Video)

The comments are the clearest signal yet that if Lai becomes Taiwan’s next president, the cross-strait relationship is set for more challenges. Lai has been leading polls for months and has signaled that if he wins, he’ll continue policies that President Tsai Ing-wen has pursued since starting the first of her two terms in 2016.

Tsai’s fostering of closer ties with Washington, including stepping up weapons deals, has frustrated Beijing. Chinese leader Xi Jinping has ratcheted up military, economic and diplomatic pressure on Tsai over her refusal to accept Beijing’s position that both sides belong to “one China.”

China has used similar rhetoric about war with Taiwan in the past, such as after Tsai’s stops in the US in the spring. Those travels included a visit to Los Angeles, where she met House Speaker Kevin McCarthy and other US officials and lawmakers. It has also referred to figures in the Democratic Progressive Party that Tsai and Lai belong to as troublemakers before.

See: War With China Is the Threat That Defines Taiwan’s Next Election

Twice since August last year the People’s Liberation Army has held major military exercises around Taiwan — one that involved sending missiles over the democracy of 23 million people. Those drills followed the Tsai talks with McCarthy and a meeting with then-Speaker Nancy Pelosi in Taipei in August.

China has pledged to bring Taiwan under its control someday as part of its “rejuvenation” project, by force if that is what’s required.

Last weekend, Lai stopped in New York on his way to Paraguay’s presidential inauguration. He’s kept the journey low profile to avoid upsetting Beijing and show voters he can be a steady hand in cross-strait issues. Lai met with officials from the US’s de facto embassy and members of the Taiwanese community in the US.

Just before his trip, China said it would hold military drills in the East China Sea, though it didn’t explicitly link the two. Lai will stop in San Francisco on Wednesday and Thursday on his return leg, opening the door to further responses from China.

Lai said in the exclusive interview with Bloomberg Businessweek in Taipei on July 27 that “we must work to maintain the peaceful status quo.”

“We are willing to cooperate with China to advance peace and prosperity,” he said. “However, until China renounces the use of force against Taiwan, we must strengthen our military capacity and stand shoulder to shoulder with democracies to effectively deter the threats from China and secure stability in the Indo-Pacific region.”

--With assistance from Jing Li and Joel Weber.