James Andrew Lewis is a senior fellow at the Center for Strategic and International Studies, where he directs the Technology and Public Policy Program.

A common enemy provided a degree of harmony in trans-A tlantic relations during the Cold War. With its end, diverging views on economic and foreign policies and the effort to forge a single European identity have created serious tensions. These tensions obscure close economic partnerships, particularly in defense and aerospace, where both sides now depend on a trans-A tlantic industrial base, but we can no longer assume that Europe and the United States automatically share security interests. In fact, the policies of some European leaders are at times explicitly antithetical to U.S. interests. This goes beyond the dispute over Iraq. The latest point of tension involves China.

In 1989, after the People’s Liberation Army (PLA) slaughtered many hundreds of pro-democracy demonstrators in Beijing, Europe and the United States imposed arms embargoes on China. China now has become the largest arms market after the United States , and many Europeans look enviously at Russia’s billions of dollars in arms sales to the Chinese.

This alone creates pressure to lift the embargo. But commercial gain is not the only motive. There is a strong political element. European countries do not share U.S. concerns about China. Some European capitals want to counterbalance the U.S. hyperpower and create an autonomous European superpower. These Europeans find attractive a move that simultaneously reinforces the image of European independence while constraining U.S. power.

China depends on advanced Russian weaponry to modernize its military, but European arms technology will make the PLA more formidable. Europe is superior to Russia in some technologies — sensors, communications, airlift (China could be attracted to the A300M) and tactical missiles.

Some European countries hope to sell ships or aircraft , and China will use European competition to bargain down Russian prices. China also will want partnerships with Europe’s defense firms to acquire industrial skills. Transfers that improve China’s signals intelligence (sigint) capabilities, including satellite technology, or their remote sensing satellites would be of immediate concern. Dual-use technologies are less important, if only because the Chinese cannot extract their military benefit. In any case, Europe’s embargo has never forbidden dual-use exports to China.

Lifting the Tiananmen embargo is not a sensible policy. With stagnant economies, feeble militaries and falling birth rates, continental Europe faces long-term decline. Economic power has shifted to the Pacific Rim. Europe confronts immense pressures from the Islamic south. The Czechs, Slovaks and Poles may recall the 1930s, the last time they depended on European security guarantees without the United States. Europe needs trans-A tlantic integration, which is an engine for growth and security for both sides.

But the pressures — commercial, political and cultural — that often make the assertion of a European identity an exercise in anti-Americanism push for ending sanctions. China’s ill-timed anti-secession law, which guarantees a military response to any Taiwanese assertion of independence, has given Europe pause, but EU spokespersons say this is only a delay and the embargo may be lifted as early as next year.

If Europe ends its embargo on China, how should the United States respond? Congress is reportedly drafting harsh penalties that would go into effect immediately upon the embargo’s end. These penalties might resurrect the Buy-American Act or limit trade in dual-use products. These were bad ideas when they first appeared, and a European mistake does not justify reviving them.

Overreaction will not help. Congressionally-mandated sanctions will damage American security rather than hurt Europe or China. The effect of sanctions is to reduce demand for American products, forcing some U.S. companies to exit the market.

Sanctions encourage other nations to build alternative sources of supply, creating new competitors for the United States in the global market. Tight International Traffic in Arms Regulations (ITAR) controls on space technology led Europe to create an ITAR-free satellite platform and a European Components Initiative, designed to provide Europe with non-U.S. sources of key satellite components.

The result is to speed erosion of the U.S. industrial base without any compensating gain for security. It does not benefit the United States to accelerate this process. If you want to strengthen foreign industries, pass sanctions.

A better response would not lump all European countries together as opponents. It would push integration and place rebuilding the political relationship at its center. This means continued or even increased cooperation in some areas, such as space. Both sides of the aisle in Washington increasingly find this sort of nuanced policy difficult to imagine, but if we could cooperate with the Soviets in space at the height of the Cold War, we can cooperate with France or Germany.

For space, this means more cooperation in civil and commercial space activities and less in military or security space. There is no sense working with Europe on advanced military technologies if these will find their way to China.

Some joint activities will need more safeguards and other activities like the European Commission’s security space research and development projects should be avoided entirely. But we need to be judicious in strengthening areas where cooperation benefits the United States.

Galileo is one such area. We are not better off if we scrap the progress made in de-conflicting spectrum use or in addressing security concerns raised by Galileo. U.S. security would be damaged if we no longer contracted with European commercial satellite communications operators to provide crucial services for our military. Nor do we gain from banning participation in the Joint Strike Fighter or in missile defense.

European partners bring technological skills and resources that strengthen U.S. security. Existing technology safeguards for Joint Strike Fighter and other programs already are tough. These programs can continue without increased risk if Europe lifts sanctions.

The ambitious U.S. agenda for space exploration is best advanced by international cooperation (including cooperation with China). Cooperative, open, transnational scientific enterprises are more productive than closed national efforts. We are more likely to succeed if we can repeat the success (if not the model) of the space station and form partnerships with other space faring nations that brings their skills and resources to bear on exploration.

In commercial space activities, we continue to damage U.S. security through overly restrictive export controls. Tight control makes sense for a few technologies (such advanced sensors), but the argument that the technologies used in a commercial communications satellite will help military programs is frivolous. One problem for the United States in designing a response to the Europeans is that we do not, after years of effort, have the ability to distinguish between civil and military or sensitive and mundane in terms of deciding what technology needs to be restricted.

If Europe lifts the embargo, arms exports will occur under an amorphous European Union Code of Conduct that calls for respect for human rights and avoiding sales “if there is a clear risk that the intended recipient would use the proposed export aggressively against another country or to assert by force a territorial claim.”

Some European nations take the code seriously, and the United States can better influence how and what European nations will sell to China if it strengthens trans-A tlantic ties.

The best outcome for the United States , for Asia and for Europe is to maintain the arms embargo. But it is not in our interest to let European action provoke us into a response that weakens NATO or diminishes the benefits to the United States of the trans-A tlantic relationship. If Congress wants to punish Europe, it should find something that does not hurt U.S. security or economic strength.

Neither we nor the Europeans have worked out the parameters of our new relationship, but we should not expect them to repent and return to the fold. Our national interest requires a new and more complex engagement with Europe. The best response is to continue to work with our friends to shape this engagement as the form and nature of the new European state becomes clearer.