After years of hampering progress in American-Russian relations, ahead of the NATO summit in Lisbon, Portugal this week the United States agreed to compromise and assure the Russians that the ballistic missile defense shield planned for Central Europe really wasn’t aimed at them. The Obama Administration agreed to construct a simpler version of the shield but now Turkey, which is supposed to host its early warning radar systems, could spoil everything.

While ratification of the latest nuclear arms reduction treaty signed by Presidents Barack Obama and Dmitri Medvedev in Prague this spring remains in doubt, the warming up of the Arctic is prompting the Russians to boost their military presence in the region where vast resources of oil and natural gas await exploitation. Russian bomber planes are regularly intercepted over European airspace while last September, the Royal Navy reported that a Russian submarine had been caught stalking one of its own subs.

Frustrated with the procrastinated New START negotiations and still hoping to “reset” relations with Russia earlier this year, the Obama Administration offered to move parts of the European missile shield which Moscow believed threatened to undermine its nuclear posture. Russia was invited to participate in the project instead and President Medvedev is attending the Lisbon summit to discuss the future of security cooperation in Europe.

But Turkey, now a regional power, is reluctant to offend Iran at which the missile shield is so obviously aimed. The country, along with Brazil, negotiated a nuclear fuel exchange agreement with Tehran in May — one that was promptly rejected by the Western allies who considered the newfound Iranian willingness to compromise little more than a stalling tactic.

Turkey is less skeptical of Iran however while recent American criticism of its more eastward policy hasn’t helped to foster a healthy climate for cooperation. President Obama, in fact, accused the Turks of not having acted as an “ally” when they voted against United Nations sanctions on Iran two months ago. His administration threatened to withhold the sale of drone attack craft to Turkey at the time.

The Turks have submitted a number of conditions to be met if they are to host the missile defense radars: the system should cover all of Turkish territory; debris of intercepted missiles should not come down on Turkish soil and all references to Iran must be eliminated. The United States could probably have agreed to these terms before Prime Minister Recep Tayyip Erdoğan added another — that Turkey should have command of the system. That’s unacceptable to the Americans.

There are alternatives to Turkey for the radar system but sidelining it now would come as another major blow in American relations with this essential NATO ally. President Obama should not interpret Erdoğan’s demands as Turkish stubbornness. Rather, the country is waking up to its potential and discovering its new place in the Middle East. The president has to recognize that the alliance has changed by granting the Turks some measure of control over the system. Turkey can’t be taken for granted anymore. What is more, if his administration is to make any progress with regard to Iran, Obama needs the Turks to act as middleman.