United States intelligence agencies recently detected China’s military shifting road-mobile ballistic missiles closer to its southern coast near the disputed Senkaku Islands amid growing tensions between Beijing and Japan over the islands dispute.

U.S. defense officials said the movements are being watched closely as China’s military is also holding large-scale military exercises that some fear could be a trigger for a conflict with Japan that could involve U.S. forces.

The officials did not provide details of the missile movements that were tracked by U.S. aircraft, ship-based, and satellite surveillance systems in the region.

Disclosure of the missile movements comes as White House national security adviser Tom Donilon on Monday met in Seoul with China’s state councilor Liu Yandong. The two were in South Korea to attend the inauguration of South Korean President Park Geun-hye.

Tensions remain high between Japan and China over Tokyo’s nationalization last year of several uninhabited islands between Okinawa and Taiwan called the Senkakus. China claims the islands as its territory. At issue are large undersea oil and gas deposits sought by both energy-poor countries.

The officials confirmed the missile movements near the provinces of Zhejiang and Fujian after Chinese press outlets first reported them.

The most recent report appeared in the Hong Kong newspaper Oriental Daily News, a non-Chinese owned outlet that quoted a military source as saying the missile deployments included new solid-fueled DF-16 road-mobile missiles.

The Feb. 21 report said the People’s Liberation Army Second Artillery Corps, which operates missile units, were preparing to target the disputed Senkaku Islands as well as U.S. military bases in Okinawa.

The Daily News stated that the missile movements were signs the PLA is "preparing for the worst regarding the territorial dispute between China and Japan over the Senkaku Islands."

The report also stated that the DF-16 is capable of defeating U.S.-made Patriot missile batteries that are deployed at U.S. and Japanese military bases in the region. The DF-16 is said to be armed with multiple warheads.

According to the report, the PLA navy near the Senkakus is part of China’s "trump card" weaponry—niche military capabilities that could allow a weaker force to defeat a stronger one.

The U.S. newsletter East-Asia-Intel.com reported Feb. 13 that China’s military appeared to be making war preparations by holding large-scale exercises around the Lunar New Year, including live fire artillery and air force bombing runs.

The newsletter said state media also reported large-scale troop movements and maneuvers near the coastal Fujian and Zheijiang provinces, the areas closest to the Senkakus.

John Tkacik, a former State Department specialist on China, said Chinese television recently reported that PLA missile forces practiced saturation bombing exercises that used for the first time an automatic launch system that could fire 10 warheads accurately on one target.

"The Pentagon and the Japanese defense ministry already take the PRC ballistic missile threat to U.S. forces in the Taiwan Strait and Ryukyus seas very, very seriously," Tkacik said. "If U.S. surveillance and reconnaissance assets show significant redeployments of road-mobile missiles, including DF-16s on China's east coast, U.S. and Japanese forces have to respond with far higher levels of threat readiness, and that sort of thing can put the gathering crisis in the Senkakus area on a hair-trigger."

Regarding China-Japan tensions, a Chinese warship aimed weapon-targeting radar at a Japanese warship, drawing protests from Tokyo. Such radar illumination at sea is often regarded as a hostile act in military parlance.

U.S. officials fear the dispute could lead to a small-scale military confrontation that might spiral into a major conflict.

The U.S. military is committed to defending Japan in any conflict despite Obama administration assertions that it takes no sides in territorial disputes.

China has been building up its short- and medium-range missile forces in the region for at least a decade. U.S. intelligence agencies estimate the total number of missiles in the region is between 1,200 and 1,500 missiles.

They include mainly DF-15 and DF-11 short-range missiles. Taiwan government sources have reported that China also has deployed longer-range DF-21s in the region.

A variant of the DF-21 is a special anti-ship ballistic missile designed by Beijing to sink U.S. aircraft carriers and it is one of the main reasons for the Pentagon’s buildup in Asia to counter what it calls anti-access and area-denial weapons.

A Pentagon spokesman declined to comment on the recent missile movements.

Richard Fisher, a Chinese military affairs specialist, said the deployment of DF-16s is in its third year and indicates the PLA "has deployed up to three brigades of this reported 800-kilometer to 1,000 kilometer-range missile."

"The DF-16 is a development of the DF-11 short range ballistic missile; it simply places the modular warhead section of the DF-11 on a much larger booster stage," said Fisher, who is with the International Assessment and Strategy Center.

"This means it could be armed with many types of warheads, including nuclear, electromagnetic pulse, fuel-air explosive, and anti-airfield submunitions. It should be expected that it eventually will have a maneuverable anti-ship warhead as well."

Fisher said China is also moving toward deployment of a new, nuclear or conventional-tipped 3,000-kilometer range missile dubbed the DF-25.

"China's goal is to overwhelm the United States and its democratic allies with new missiles, much as it has overwhelmed Taiwan with shorter range missiles," Fisher said.

The growing Chinese missile threat comes as the Obama administration unilaterally retired its theater-range nuclear Tomahawk cruise missiles even as China is moving ahead with new missiles of that range.

"It is now imperative that the United States get back into the medium- and intermediate-range missile business and to help some of our allies to do the same, in order to deter China," Fisher said.

"Only when the U.S., Japanese, and South Korean navies have enough long-range anti-ship ballistic missiles to take out China's shiny new navy will Beijing wake up and reconsider its course of increasing aggression," he said.

Meanwhile, China’s state-controlled media has been ramping up rhetoric indicating China is preparing for a conflict over the Senkakus. Large-scale military exercises have been held in recent weeks and Chinese leaders have been reported as telling troops to prepare for combat.

Chinese leader Xi Jinping said during a visit earlier this month to a military command that Chinese forces should be "expanding and deepening" combat readiness. Xi in December also called for intensifying "real combat" skills.

The United States and Japan held combined military exercises that ended Feb. 15 called "Exercise Iron First." Chinese state media reported the war games were practice for "island seizure" operations and preparations for a conflict with China over the Senkakus.

More than 1,000 Marines and 280 Japanese Self-Defense Forces troops took part in the maneuvers at Camp Pendelton, Calif.

China on Monday announced that its navy has deployed the first of a new generation of radar-evading stealth warships, called a Type 056 frigate.

The official Chinese military newspaper PLA Daily stated that the new frigate will be deployed in large numbers and features low radar observability and electromagnetic signatures.

The new warship will be used for escort and anti-submarine missions.

The PLA navy also announced that it would conduct military exercises in the northern Yellow Sea near the major military port of Dalian beginning Wednesday.

Chinese state television CCTV reported Feb. 13 that PLA air force units in northeastern China carried out an "emergency war preparedness exercise."

Three PLA warships completed a major open-ocean exercise Feb. 15 after 18 days at sea. The ships, a missile destroyer and two frigates, sailed in the East China Sea, where the Senkakus are located, as well as the Yellow Sea.