Soldiers of armored infantry battalion Panzergrenadierbataillon 122 of the Bundeswehr, the German armed forces, in Lithuania | Johannes Simon/Getty Images Opinion Why NATO needs a European pillar If Europe tries to protect the alliance only by ‘buying’ American commitment through increased defense spending, it will fail.

Europeans have every reason to worry about U.S. President Donald Trump. He has declared NATO "obsolete." He's spoken more glowingly about Russian President Vladimir Putin than about most Western European leaders. And he's suggested he will apply his transactional vision of diplomacy to his country's alliances. A president who has unabashedly made “America First” his guiding principle is telling Europeans America's commitment to them will depend on their willingness to pay for it.

The Continent's leaders should listen carefully. For too long, European countries have not been serious enough about their own defense; most spend much less than the 2 percent of GDP goal set by NATO. If they do not change course, a president who has little understanding of soft power and, in his own words, only respects “strength,” will not take them seriously.

A European security landscape defined in bilateral talks between Russia and the U.S. is a serious possibility, one that would be terrible news for the Continent. Trump might care most about fighting Islamic terrorism; for Russia, the priority remains dividing Europe to gain the upper hand.

If Europe’s only response is to “buy” American commitment through increased defense spending — as NATO chief Jens Stoltenberg has indicated alliance members should do — it will fail. NATO cannot sustain itself as a political alliance if it is guided by monetary transactions. Its European members must show unity of purpose and vision: The time has come to create a European pillar of NATO.

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Today, there is no shared vision of what NATO stands for, and apparently little interest in the White House for the principles that gave substance to the NATO security commitment during the last 67 years. The transatlantic solidarity defined by Article 5 of NATO's founding treaty is only credible if it is underpinned by a set of shared values.

NATO is about North America's engagement in Europe, and Europeans, working with Canada, must take the initiative in proposing a vision adapted to the 21st century. Otherwise, they run the risk that a president who has little time for the Continent will see his European allies simply as adjuncts to an "America First" strategy — and blatantly ignore their interests.

The idea of a European pillar is not new, but was deemed unnecessary for many years because the alliance's members shared a solid consensus on its functions. As a proposal, a pillar now makes sense in terms of realpolitik. With a U.S. president who appears more than happy to play nations against one another, European countries are unlikely to make themselves heard unless they can present a coherent, united position.

The move would also benefit intra-European political dynamics. Europeans are unlikely to support increased defense spending if it is perceived simply as a response to American bullying and support for Washington's somewhat incoherent policies. Increased effort must come with a renewed sense of political ownership for NATO's European members. A stronger EU that regains political momentum by making its own security a political priority, is an indispensable partner to a strong NATO.

The specifics of a more integrated effort, whether a European headquarters or an expanded role for the European Defense Agency, or ideas to implement the EU global strategy in the area of security and defense as agreed by EU member countries in November, should be discussed between EU nations.

National governments will want to retain a central role in matters of national security, but the European institutions can help coordinate the effort and give it a broader European dimension.

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A European pillar will first have to decide on its membership. Germany and France, whose military capacities are increasingly compatible and complementary, should take the lead once elections in both countries have taken place.

A caucus needs to emerge within NATO. It should include the six founding members of the EU, as well as more recent members, which could agree on two founding principles: that the emergence of a European pillar is made necessary by the changed strategic landscape; and that a European pillar should be conceived as a means to strengthen NATO, not as an alternative to it. In fact, one of its key goals will be to keep the U.S. engaged.

That core group should in time be opened to other members of the EU and should establish close consultation mechanisms with EU non-NATO members, such as Sweden, and with NATO non–EU members, such as Norway and Turkey.

An informal political approach is probably the only viable path to this European pillar, since a formal institutional approach would likely stall very quickly. A formal arrangement with Turkey, for example, will remain difficult until its problems with the bloc — the question of Cyprus' reunification remains a sore point — are solved.

And within the EU, serious differences have emerged on what role the Union should play in its own defense. Separated from the question of EU membership, a European pillar within NATO could bring countries with varying degrees of EU adherence into the fold. The United Kingdom — one of the Continent's most important military powers — for example, is about to leave the EU but could find its strategic interests best served by a close relationship with the new group.

In an era of rising nationalism, creating a European pillar of NATO may sound ambitious. But opinion polls show that Europeans, while critical of many aspects of the EU, consider defense to be an area that warrants more, rather than less, cooperation. The EU will not get out of its present malaise by renouncing its ambitions. On the contrary, it needs to be more ambitious if it wants to respond to the security concerns of its citizens. The exceptional circumstances confronting Europe require an exceptional response.

Jean-Marie Guéhenno is president and CEO of International Crisis Group, the independent conflict prevention organization.