You wouldn't have thought America is in a mood to reach for the moon with China. Certainly not after George W. Bush's recent summit with Hu Jintao, when the Chinese president didn't lend any meaningful support for international efforts to tackle North Korea and Iran's nuclear-weapons programs. But that's precisely what China is gleefully claiming as a result of a little-noticed by product of the April 20 summit. Beijing, it seems, wants the world to believe that the next lunar mission will be a joint Sino-U.S. program -- and the White House has given it the ammunition to do so.

It all stems from a post-summit press briefing by Deputy National Security Advisor Faryar Shirzad and National Security Council Acting Senior Director Dennis Wilder. They told journalists that President Bush had agreed to dispatch NASA Administrator Michael Griffin to China "to begin to talk about lunar exploration with the Chinese." That marks a major shift away from America's longstanding policy of avoiding most kinds of contact with China's military-run space program, largely for fear of allowing sensitive dual-use technology to fall into Beijing's hands. Until now, that policy has been so strict that the U.S. even successfully pressured the European Space Agency in 2004 to limit China's access to the Galileo global-positioning system it is developing.

So it wasn't long before alarm bells began ringing in Washington over a policy change that doesn't seem to have been fully discussed within the Bush administration. "Did you see what they sneaked into the press briefing?" one administration official asked me in disbelief. "What will the Europeans think after we threw a fit about Galileo?" Under sharp questioning before a Senate committee, Mr. Griffin was evasive about what his trip would entail, saying it was too early to "hazard a guess as to what our relationship in the long term would be."

Apart from the brief reference to cooperating over "lunar exploration" in the April 20 briefing, which was bracketed together with more mundane issues such as dealing with space debris, there's no sign anyone in the administration is thinking seriously about a joint lunar mission. But that hasn't stopped Beijing from portraying it as a done deal. "China, U.S. to join hands in lunar probing," proclaimed a headline last week in the People's Daily, the Communist Party's official mouthpiece. The article also pointed to the "coincident landing time" of planned missions to the moon by China in 2017 and the U.S. in 2018.

What's rather more advanced is the idea of helping China modify the hatch on its Shenzhou space capsule so that it can dock with the International Space Station and U.S. spacecraft. Republican Congressman Mark Kirk, cofounder of a Congressional caucus seeking cooperation with Beijing known as the "U.S.-China Working Group," returned from a recent trip to Beijing with a Chinese proposal that this would help "rescue" U.S. astronauts in an emergency.

But even that is causing concern at the Pentagon. Defense officials see enhancing the People's Liberation Army's familiarity with American space systems as particularly unwise, given that the U.S. depends on space satellites for approximately 90% of its military communications, intelligence, and command and control of military operations. A European space expert also pointed out that China's Shenzhou capsules are fitted with military sensors -- one reason the Europeans did not want to get involved with the Shenzhou program. Cooperating with Beijing could violate International Governmental Agreement setting up the Space Station, which stipulates it is to be used "exclusively for peaceful purposes."

Space cooperation with China can take more mundane forms. America's National Center for Atmospheric Research already uses U.S. weather satellites to collect data on ocean temperatures from Chinese scientific vessels near the equator. There can be few objections to space cooperation with Beijing in areas like this, as well as monitoring the environment and pollution levels. But there are many areas of space technology central to manned space flight, such as global positioning, communications and orbital trajectory targeting, which have direct military applications. Other technologies used in space flight and exploration are on the U.S. export control list, such as robotics, advanced materials and new battery technology. These are all areas where the U.S. is the world leader and China is anxious to get its hands on America's proprietary engineering processes.

Remember too, that Beijing has a history of using U.S. space technology to enhance its military capabilities. A 1999 investigation by former California Congressman Christopher Cox found that China had used technical assistance from U.S. companies to uncover a series of problems with the nose cone in its Long March series of rockets used to launch commercial satellites into space. Mr. Cox argued that assistance helped China avoid similar problems with its intercontinental ballistic missiles, which are capable of delivering nuclear warheads as far as the U.S.

That highlights the dangers in cooperating with China's military-run space program. Giving Beijing access to technology which it can integrate into weapons systems could allow it to target not only America's democratic allies and friends in Asia -- Taiwan, Japan and India in particular -- but ultimately America itself, too. Cooperating with China over space may seem innocuous, and in some limited areas, it is. But past experience shows that if this extends to sharing technology -- as any kind of lunar cooperation certainly would -- it will be a one-way street, in which Beijing ends up as the only winner.

John Tkacik a senior research fellow at the Heritage Foundation in Washington, D.C., is a retired officer in the U.S. foreign service who served in Beijing, Guangzhou, Hong Kong and Taipei.