China has been using coercive tactics in pursuit of territorial and maritime claims in the South and East China Seas, as well as along its border with India and Bhutan, the Pentagon has said.

China is engaged in hotly contested territorial disputes in both the South China Sea and the East China Sea. Beijing has built up and militarised many of the islands and reefs it controls in the region. Both areas are stated to be rich in minerals, oil and other natural resources and are vital to global trade.

China claims almost all of the South China Sea. Vietnam, the Philippines, Malaysia, Brunei and Taiwan have counterclaims over the area.

"China's leaders use tactics short of armed conflict to pursue China's objectives. China calibrates its coercive activities to fall below the threshold of provoking armed conflict with the United States, its allies and partners, or others in the Indo-Pacific region," the Pentagon said in its annual report on China to the Congress.

China has been fast expanding military and economic influence in the Indo-Pacific region, triggering concern in various countries of the region and beyond.

"These tactics are particularly evident in China's pursuit of its territorial and maritime claims in the South and East China Seas as well as along its border with India and Bhutan," said the report titled ''Military and Security Developments involving the People's Republic of China 2020'' that was released by the Pentagon.

"Tensions with India persist along the northeastern border near the Indian state of Arunachal Pradesh, which China asserts is part of Tibet and therefore part of China, and near the Aksai Chin region at the western end of the Tibetan Plateau," the Pentagon said in its report to the Congress.

The report, however, makes no mention of the latest stand-off between India and China in Ladakh.

The report also said that the Chinese military was pressing to double its 200-plus nuclear warheads within a decade with the ability to launch them aboard ballistic missiles by land, sea and air. A Pentagon official said that although China remains far behind the US in terms of nuclear warheads, the acceleration shows Beijing moving from its traditional "minimum deterrence posture" to full-fledged competition.