By Sakura Murakami

TOKYO (Reuters) -China said it was troubled by Japan's military build up and Tokyo took aim at Beijing's military ties to Russia and its suspected use of spy balloons during the Asian powers' first formal security talks in four years on Wednesday.

The talks, aimed at easing tensions between the world's second- and third-largest economies, came as Tokyo worries that Beijing will resort to force to take control of Taiwan in the wake of Russia's attack on Ukraine, sparking a conflict that could embroil Japan and disrupt global trade.

Japan in December said it would double defence spending over the next five years to 2% of gross domestic product - a total of $320 billion - to deter China from resorting to military action. Beijing, which increased defence spending by 7.1% last year, spends more than four times as much as Japan on its forces.

Tokyo plans to acquire longer range missiles that could strike mainland China and to stock up on other munitions it would need to sustain a conflict alongside the large U.S. force it hosts.

"The international security situation has undergone vast changes and we are seeing the return of unilateralism, protectionism, and a Cold War mentality," Chinese Vice Foreign Minister Sun Weidong said at the start of the meeting in Tokyo with Japanese Deputy Minister of Foreign Affairs Shigeo Yamada.

China is Japan's largest trading partner, accounting for around a fifth of its exports and almost a quarter of its imports. It's also a major manufacturing base for Japanese companies.

“While relations between Japan and China have a lot of possibilities, we are also facing many issues and concerns," Yamada told Sun.

He pointed to their territorial dispute over uninhabited islands in the East China Sea known as the Senkaku in Japan and Diaoyu in China, Beijing's recent joint military drills with Moscow and the suspected Chinese surveillance balloons spotted over Japan at least three times since 2019.

Following the downing of a suspected Chinese spy balloon by the United States, Japan last week said it planned to clarify military engagement rules to allow its jet fighters to shoot down unmanned aircraft that violate its airspace.

In a statement released after the meeting, Japan's foreign ministry said it had also stressed the importance of peace and stability in the Taiwan Strait.

The two countries had agreed to try and establish a direct communication hotline "around spring", and to strengthen dialogue between their senior security officials, it added.