As President Obama prepares to welcome Chinese President Hu Jintao to the White House this week, China is debuting new military capabilities and issuing threats of an arms race with Japan.

When Hu arrives on January 19, he and Obama will discuss East Asian hotspots, including North Korea’s nuclear program and its artillery assault on the South in November. Obama should maintain strong U.S. military support for our allies in Asia, and resist pressure from Hu to return to the six-party talks, even if China offers to make concessions on its support for North Korea.

Joining the U.S. and the international community in isolating the increasingly erratic, violent and nuclear North Korea is in China’s own interests, and Beijing should be willing to exert pressure on its neighbor without inducements from Washington. Yet China steadfastly refuses to condemn North Korea’s attacks on the South, emboldening the Kim regime to act with impunity.

China’s ambivalence towards North Korean aggression follows a recurring rift in Sino-U.S relations that developed in January 2010, after the Obama administration announced a bold $6.4 billion arms sale to Taiwan, including 114 Patriot defensive missiles. On the eve of the deal, China fired off rockets to signal its disapproval, and afterwards, the incensed Chinese government cut off military cooperation with the U.S. Although the sale was a boon for Taiwan, the Obama administration showed deference to China by excluding the sale of the F-16 fighter jets the Taiwanese have requested.

U.S. military support for Taiwan isn’t the only reason for angst in Beijing. On December 15, Japan released its National Defense Program Guidelines, reorienting its military strategy. The document notes several changes in the global environment, including a decline of U.S. influence and a rise of emerging countries such as China and India. It described North Korea as Japan’s biggest threat and China as a “country of concern.”

As a result, Tokyo has committed to increasing cooperation with the U.S. military and enhancing its missile defense capabilities. A Chinese diplomat responded by saying, “Japan’s new military investments are going to transform the military balance in the region…China will have no choice but to respond by enhancing its own capabilities.”

In October, the U.S. and Japan conducted a joint missile defense test, intercepting a missile from an Aegis cruiser off the coast of Hawaii. Although Washington and Tokyo had plans to continue close collaboration on missile defense, a joint research program to develop software for the Aegis system collapsed three days ago after the U.S. and Japan failed to agree on conditions about selling the technology, which may portend problems for other joint projects.

Meanwhile, China is modernizing every branch of its military. Earlier this month, leaked photos in The Wall Street Journal revealed a fifth-generation Chinese stealth fighter that bears an alarming resemblance to the F-35 Joint Strike Fighter.

And not only that, also recently, Admiral Robert Willard, head of U.S. Pacific Command, reported that China’s Dongfeng 21D anti-ship ballistic missile has achieved “initial operational capability,” meaning China has made great progress on a missile that could strike U.S. aircraft carriers supporting South Korea, Japan, or Taiwan.

Despite Chinese officials’ insistence that they do not pose a threat to any country, Beijing continues to increase the quantity and quality of its nuclear arsenal, and pursue the most active land-based cruise and ballistic missile programs in the world. In 2007, China successfully launched an anti-satellite weapon, destroying one of its own satellites, proving it can attack U.S. assets in space.

Regardless of China’s intentions, it has a large and growing capability to project power abroad. China is preparing to fight, and its agenda may not be consistent with U.S. national interests.

In the face of China’s military advancements, and its increasing resistance to U.S. allies in East Asia, the Obama administration must show strength. It must continue military support to South Korea and Taiwan, and recommit to missile defense cooperation with Japan.

China will likely continue to test Obama’s resolve. To prevent a conflict, he must make clear that we are willing and able to defend our democratic allies from aggression.

Rebeccah Heinrichs is an adjunct fellow at the Foundation for Defense of Democracies.

Rebeccah Heinrichs is a fellow at the Hudson Institute where she provides research and commentary on a range of security issues and specializes in missile defense and nuclear deterrence. She is also contributing editor at Providence Magazine. Follow her on Twitter, @RLHeinrichs.