BEIJING — Chinese President Xi Jinping said China reserves the option of "taking all measures necessary" against "interference by outside forces" on the issue of Taiwan.

In a wide-ranging speech Sunday, Xi spoke firmly about China's resolve for reunification with the self-governed island, which Beijing considers part of its territory.

He was speaking at the opening ceremony of the ruling Communist Party of China's 20th National Congress, held once every five years.

"We will continue to strive for peaceful reunification with the greatest sincerity and the utmost effort," Xi said in Chinese, according to an official translation. "But, we will never promise to renounce the use of force. And we reserve the option of taking all measures necessary."

"This is directed solely at interference by outside forces and a few separatists seeking Taiwan independence," he said, emphasizing that resolving the Taiwan question is a matter for the Chinese to resolve.

Tensions around Taiwan intensified this summer after U.S. House Speaker Nancy Pelosi's controversial visit to the island.

The visit came despite warnings from China, which maintains the island should have no right to conduct foreign relations. The U.S. recognizes Beijing as the sole legal government of China, while maintaining unofficial relations with Taiwan.

On Sunday, Xi gave the issue of Taiwan greater prominence in his speech than he had five years ago at the party';s 19th National Congress.

The high-level meeting decides which officials will become the leaders of the party, and ultimately, of China.

Next weekend, the names of the new core team around Xi are due to be announced. State titles such as president and premier are officially confirmed at an annual meeting of the Chinese government, typically held in March.