TAIPEI (AFP) -- Taiwanese President Lai Ching-te vowed Thursday to “resist annexation,” as China exerts growing military and political pressure on the self-ruled island it claims as part of its territory.

China has not ruled out using force to bring the democratic island under its control, which Lai and his government oppose.

“I will also uphold the commitment to resist annexation or encroachment upon our sovereignty,” Lai said under grey skies during Taiwan’s National Day celebrations.

Beijing has ramped up pressure on Taiwan to accept its territorial claims and relations have remained tense under Lai, who took office in May.

A senior United States (US) administration official said Wednesday that China may use the National Day celebrations “as a pretext” for military exercises.

Lai has been more outspoken than his predecessor Tsai Ing-wen in defending Taiwan’s sovereignty, angering Beijing, which calls him a “separatist.”

Beijing accused Lai on Tuesday of “malicious intent to escalate hostility and confrontation” after he said China was not the “motherland” of Taiwan.

“Our determination to defend our national sovereignty remains unchanged,” Lai said Thursday, in front of an audience that included Tsai and pro-independence former Taiwan president Chen Shui-bian.

“Our efforts to maintain the status quo of peace and stability in the Taiwan Strait remain unchanged,” Lai said in front of the Presidential Office.

Taiwan on alert

Taiwan was on alert for Chinese military drills near the island on National Day after observing “some maritime deployments,” a senior security official told Agence France-Presse (AFP) on Wednesday.

China maintains a near-daily military presence around Taiwan and has held three rounds of large-scale war games in the past two years, deploying aircraft and ships to encircle the island.

“Even though we have not seen significant military activity or exercises following previous 10/10 speeches, we are prepared that Beijing may choose to use this as a pretext this year,” the senior US administration official told reporters.