BEIJING, July 6 (Reuters) - Chinese President Xi Jinping on Thursday urged the military to deepen war and combat planning to increase the chances of victory in actual combat, Xinhua news agency said, renewing his call to troops to safeguard China's sovereignty and territory.

Xi said the world has entered a new period of turmoil and change and China's security situation has become more unstable and uncertain, according to state-run Xinhua, in comments he made to troops while on an inspection tour of the Eastern Theater Command.

The Eastern Theater Command, headquartered in Jiangsu province, is responsible for the security of eastern China, including the East China Sea and the Taiwan Strait.

Earlier this year, Xi, in comments after securing a precedent-breaking third term as president, called on China to step up its ability to safeguard national security and turning its military into a "Great Wall of Steel".

On Taiwan, the democratically governed island which China claims as its own, China must oppose pro-independence and secessionist activities and the interference of external forces, he said at the time.

In particular, China has repeatedly called on U.S. officials not to engage with Taiwanese leaders, viewing it as support for Taiwan's desire to be viewed as separate from China.

Since the visit of the then-U.S. House Speaker Nancy Pelosi to Taiwan in August last year, China has staged war games around the island and conducted drills and live firing in the region.

China has never renounced the use of force to bring Taiwan under its control. In 2005, it passed a law giving Beijing the legal basis for military action against Taiwan if it secedes or seems about to.

Xi's call to step up combat-readiness came as U.S. Treasury Secretary Janet Yellen arrived in Beijing for talks aimed at easing tensions between the U.S. and China.

"We must persist in thinking and handling military issues from a political perspective, dare to fight, be good at fighting, and resolutely defend our national sovereignty, security, and development interests," Xi told the Eastern Theater Command.

In April, Xi inspected the Guangdong-headquartered Southern Theater Command, whose sphere of responsibility includes the South China Sea, much of which is claimed by Beijing.

He similarly stressed the need to deepen military training and preparation, just as the Chinese navy increased its assertiveness with training missions and drills to counter expanding U.S. maritime presence in the region.