Beijing,  During his opening speech Sunday morning at the start of the Party Congress, Chinese leader Xi Jinping vowed to speed up efforts to build the People's Liberation Army (PLA) into a "world-class military", local media reported.

To achieve that, the Chinese military should uphold the party's "absolute leadership", modernise its theory, organisation, personnel and weapons, Xi was quoted as saying by the CNN.

He pledged to improve the PLA's ability to safeguard national sovereignty, security and development interests, and to "effectively fulfill the mission of the people's army in the new era."

To do this, the military must build a strong system of strategic deterrence, increase the proportion of combat forces in new areas and deepen military training for real combat, he said.

Xi also raised the possibility of confrontation when discussing democratic Taiwan -- which the Communist Party claims as its territory, despite never having controlled the self-governing island, CNN reported.

"We will continue to strive for peaceful reunification with the greatest of sincerity and the upmost effort, but we will never promise to renounce the use of force and we reserve the option of taking all measures necessary," Xi said.

Xi gave a stern warning on Taiwan during his speech on Sunday, saying China would achieve reunification with the self-governing island by force if necessary.

He added that his words were "directed solely at interference by outside forces and a few separatists seeking Taiwan independence".

China's ruling Communist Party claims Taiwan as its territory, despite never having controlled it.

Xi's remarks on Taiwan drew the greatest level of applause through his speech, which ran just short of two hours, CNN reported.