A Beijing official warned on Wednesday that if Taiwan pushes toward independence, China will take “dramatic measures,” adding that Taiwan’s provocations and foreign meddling might worsen next year.

China claims democratically controlled Taiwan as its own territory and has increased military and diplomatic pressure in the last two years to bolster its claim, causing outrage in Taipei and anxiety in Washington.

Ma Xiaoguang, spokesperson for the Taiwan Affairs Office, told a media conference that China was eager to do all possible to achieve peaceful reunification with Taiwan, but that if any red lines on independence were crossed, China would respond.

“If separatist forces in Taiwan seeking independence provoke, exert force or even break through any red line, we will have to take drastic measures,” Ma said.

Taiwan has emerged as a key factor in strained relations between China and the United States, the island’s most important international backer and arms supplier despite the absence of formal diplomatic ties.

China regularly describes the island as the most sensitive issue in its ties with the United States.

Ma said provocation by pro-independence forces and “external intervention” could grow “sharper and more intense” in coming months.

“Next year, the Taiwan Strait situation will become more complex and severe,” he said.

Beijing has sent repeated air missions over the Taiwan Strait in recent months to pressure Taiwan. It has said it will not give in to threats.

While the United States recognizes only one China, it is required by law to provide Taiwan with the means to defend itself and has long followed a policy of “strategic ambiguity” on whether it would intervene militarily to protect Taiwan in the event of a Chinese attack.

The defeated Republic of China government fled to Taiwan in 1949 after losing a civil war with the Communists, who established the People’s Republic of China.