China is building up intermediate-range ballistic and cruise missiles that pose a growing threat to Guam, the strategic Pacific island that is central to the U.S. military pivot to Asia, according to a congressional report made public Tuesday.

Six different missiles capable of reaching Guam from China are deployed or in late stages of development, says the report by the U.S.-China Economic and Security Review Commission.

They include the DF-26 intermediate-range missile that Beijing unveiled during a recent military parade, and dubbed the "Guam-killer," that can be armed with both nuclear and conventional warheads.

"The DF-26 is China’s first conventionally-armed IRBM and first conventionally-armed ballistic missile capable of reaching Guam," the report said, noting that its inclusion in a September 2015 military parade in Beijing "indicates it has likely been deployed as an operational weapon."

The report put the risk of a Chinese attack on Guam as low.

Pentagon spokesman Cmdr. Bill Urban said the Defense Department continues to monitor China’s military modernization and missile program. "Potential threats are continually factored into defense planning and capability investments," he said, adding that the Pentagon’s most recent report on the Chinese military noted efforts by Beijing to target Guam with missiles.

However, publication of the report comes amid rising U.S.-China tensions in the South China Sea. On Tuesday, the Pentagon announced that a U.S. guided missile destroyer, the USS William P. Lawrence, sailed within 12 miles of a disputed island occupied by China in the South China Sea.

It was the Navy’s third "freedom of navigation" operation since October intended to challenge Chinese claims to the disputed islands and reefs.

A Chinese government spokesman criticized the warship passage as "threatening" China’s sovereignty over the islands. China is claiming some 90 percent of the South China Sea as its maritime territory.

The Philippines’ government has challenged China’s claims to the Spratlys at an international court that is expected to rule against China in the coming weeks.

The court ruling is expected to further intensify military tensions in the region.

The South China Sea is a key strategic waterway linking the Indian and Pacific Oceans where an estimated $5 trillion in trade transits annually.

The report identified other new missiles capable of hitting Guam as an anti-ship variant of the DF-26, and several air- and sea-launched land-attack and anti-ship cruise missiles. The missile has a range of between 1,800 miles and 2,500 miles, enough to hit Guam, which is located in the South Pacific about 1,500 miles from the Philippines.

The island is the focus of a major buildup of U.S. naval and air forces including attack submarines, strategic bombers, and long-range drones as part of the Obama administration’s "rebalance" to Asia.

"Guam … is growing in importance to U.S. strategic interests and any potential warfighting operations in the Asia Pacific, even as China’s ability to strike the island is increasing," the report, written by commission analyst Jordan Wilson, says.

"Such attacks could hold key U.S. assets stationed on Guam at risk and also disrupt their region-wide response effort, slowing deployment timetables and reducing the effectiveness of U.S. forces in the theater."

One worrying sign outlined in the report is China’s increased naval spying near Guam through PLA navy maritime intelligence-gathering ships.

"These ships likely have equipment enabling them to collect signals intelligence and map the ocean floor, suggesting the PLA Navy may be preparing for more routine naval operations in the vicinity of Guam in the near future," the report said.

By threatening Guam with missile strikes, China’s communist leaders might be more willing to resort to military force in a crisis and limit the United States’ ability to deter conflict, the report said.

The report suggests the United States harden military facilities on Guam against missile attack, develop advanced missile defenses, and rethink continued adherence to the 1987 U.S.-Russia Intermediate-range Nuclear Forces Treaty that limits the Pentagon from building missiles with ranges between 300 miles and 3,000 miles.

Rick Fisher, a China military affairs analyst, said the report should be a wake-up call for U.S. policymakers who have insisted in the past that China’s modernization poses no threat.

"For decades scores of U.S. officials have been telling Americans that a strong China is good for America and the world," said Fisher, a senior fellow at the International Assessment and Strategy Center.

"The China Commission's report blasts this delusion; a strong China is building a growing threat to the security of America and to all democracies," he said. "China is spoiling for a war in the South China Sea and if its wins, or forces the U.S. to leave Southeast Asia, it will set its sights on Guam."

Larry Wortzel, a former military intelligence officer and current commission member, said China’s military is countering the U.S. military rebalance to Asia by targeting Guam.

"The PLA [People’s Liberation Army] has developed new classes of conventional ballistic missiles to increase its capacity to strike Guam while seeking to keep any conflict below the nuclear threshold," Wortzel said.

"The PLA navy, air force, and naval air force also can target Guam with stand-off precision cruise missiles," he added. "U.S. facilities in Guam need to be hardened and protected with effective ballistic missile and cruise missile defenses."

The report says the road-mobile DF-26 is not yet a precision strike weapon but that it poses a concern if large numbers are deployed. The DF-26 anti-ship variant also has not been tested against a ship at sea but is being developed.

The drive for a missile capable of striking Guam is the result of leaders of the ruling Communist Party of China seeking capabilities to counter what they regard as U.S. military encirclement of China.

To counter U.S. and allied forces in Asia, China is developing weapons for fighting conflicts in two island chains, the first stretching from Japan, to the Philippines to the South China Sea, and the second including the Northern Mariana Islands, Guam, Palau, and eastern Indonesia.

A new air-launched cruise missile, the long-range CJ-20, is deployed on China’s newest and most capable bomber, the H-6K. The missile has a range of 932 miles and the bomber’s range is 2,175 miles.

However, the bombers lack radar-evading stealth technology and could be countered by U.S. and Japanese jets.

China’s new Type-095 nuclear attack submarines are likely to be armed with land-attack cruise missiles, along with new Luyang-III guided missile destroyers.

"Depending on their position, surface ships and submarines equipped with [land-attack cruise missiles] would be able to provide additional strike options against facilities on Guam," the report said.

China’s new YJ-18 anti-ship cruise missiles can travel up to 334 miles and could threaten U.S. naval operations near Guam if Chinese warships manage to get close enough without being detected.

The Pentagon currently has deployed one battery of the Terminal High-Altitude Area Defense missile defense system on Guam. A battery includes three launchers, 24 anti-missile interceptors, and the AN/TPY-2 radar surveillance systems.

The DF-26 missile is the most significant threat to Guam "although it likely will remain extremely inaccurate until China extends its precision strike capabilities," the report said.

The commission's report makes clear that in addition to Taiwan, Okinawa, and the Philippines, the island of Guam is now being targeted in planned barrage strikes of Chinese missiles.

"As Guam is now a frontline American territory in the battle for dominance in Asia, it is necessary that Guam receive far greater priority in U.S. defense allocations, to include early stationing of ground-based electromagnetic rail guns for terminal missile defense, the stationing for more nuclear attack submarines to [defend against] PLA navy cruise missile carriers, plus fighters and refuelers to [defend against] PLA air force cruise missile carriers," Fisher said.