On December 14, the Trump administration sanctioned Turkey’s Presidency of Defense Industry (SSB), along with key individuals involved in the purchase of the Russian-made S-400 air and missile defense system.

The sanctions authority comes from the August 2017 Countering America’s Adversaries Through Sanctions Act (CAATSA). CAATSA was designed to bind the hands of President Donald Trump to ensure that he could not unilaterally lift the sanctions placed on Russia for its interference in the 2016 presidential and congressional elections. The legislation also includes so-called secondary sanctions, which threaten countries that do business with Russia’s government-affiliated defense industries, as part of the overarching effort to decrease Russian arms exports.

Following the failed July 2016 coup attempt, Turkey sought to deepen ties with Russia, beginning with Turkish President Recep Tayyip Erdogan’s apology for downing a Russian Su-24 bomber in November 2015. Ankara’s turn to Moscow for a major weapons purchase was out of step for Turkey. Since the late 1970s, Turkish defense procurement policy has focused on negotiating offsets into major defense deals, so elements of a weapon’s production is done in Turkey by Turkish workers. The United States has supported this policy, beginning with the sale of F-16s in the early 1980s and including a number of modern programs like the assembly of U.S.-made Blackhawk helicopters in Turkey.

The American-Turkish discussions for air and missile defense have been no different. The United States offered the Patriot air and missile system, along with provisions for Turkey to eventually produce elements of the missile and associated components in iterative negotiations. Ankara has consistently pushed for additional offsets, with negotiations often stalling and then collapsing, before being resuscitated and pursued again.

Turkey broke with precedent in December 2017 when it confirmed reports that it had finalized a deal for the Russian S-400. At the time, Washington signaled to Ankara that the agreement would threaten Turkey’s participation in the F-35 program and ran the risk of CAATSA sanctions, too. To dissuade Ankara from consummating its arrangement with Moscow, the Trump administration offered the Patriot under similar terms as those offered by Russia, albeit with greater offset promises.

Both the American and Russian offers promised the rapid delivery of an off-the-shelf system, with negotiations on local work-share to be reached after delivery. Both the United States and Russia offered financing as well. The two, however, differed on the promise of work-share. Put simply, Russia reportedly offered far less than Washington.

Turkey’s selection of the S-400 is ultimately tied to the whims of Erdogan, who has sought to pursue a neutral foreign policy that disentangles Ankara from its close ties with the West. This foreign policy is, ultimately, premised on transactionalism and a now-pervasive notion that the West must accept Turkish maximalist claims—otherwise, it will be left to grapple with a recalcitrant and hostile Turkish response.

With the selection of the S-400, Ankara signaled it was willing to diversify its foreign suppliers of weapons, while also maintaining the goal of Turkish defense policy of producing its own systems. This policy ultimately means that Turkish elites view the S-400 as a stop gap until its own indigenously produced system is developed and fielded. The development of such a system is expensive and difficult, calling into question the feasibility of the project on technical and economic grounds.

For the United States, the response has been slow and uneven. The first move was to remove Turkey from the F-35 consortium and block the transfer of jets to Turkey, effectively ending Ankara’s chance of procuring the world’s only 5^th generation fighter designed for export. In parallel, Congress imposed a de-facto arms embargo on Turkey, largely in response to Ankara’s invasion of Syria in October 2019. The imposition of CAATSA sanctions is the final pillar of this three-pronged approach.

The Trump administration was not an enthusiastic supporter of CAATSA, but yielded to congressional pressure. The administration acted just before the 2021 National Defense Authorization Act (NDAA) was set to pass. The most recent NDAA includes language outlining how CAATSA sanctions are to be lifted: Ankara must give up its current S-400, end negotiations for the second regiment, and pledge not to purchase a successor system. These terms are arduous and unlikely to be greeted with enthusiasm in Ankara.

The two sides, therefore, are now in stalemate. The current U.S. sanctions are narrowly written, designed to punish the SSB, without causing spillover damage to the Turkish economy. The sanctions deny future licenses for U.S.-controlled export items for contracts that the SSB is involved in, which effectively means that Turkish procurement of U.S.-controlled equipment will be banned. Ankara does have tools to get around this ban, perhaps through a change in how it contracts with suppliers for defense projects.

The American intent was not to crater the Turkish defense industry. Instead, the goal is to deter other potential purchasers of Russian equipment and to create a pathway for these sanctions to be lifted. For this reason, the effectiveness of the sanctions will largely be determined by the actions Turkey now takes. In the past, Ankara has flirted with deepening cooperation with Russia, with Erdogan suggesting Ankara could purchase Russian fighter jets; he also has inquired about the availability of the S-500, the S-400’s successor system.

For the United States, the lifting of sanctions will depend on Turkish reciprocity. President-elect Joseph Biden will have to make the case to a skeptical Congress that the relationship with Turkey is worth the headache. This argument will have to be more sophisticated than dated claims about Turkish geography being so important that it overrides Ankara’s foreign policy choices. The S-400 issue can—and should—be treated as an arms control problem. If Ankara is serious about having sanctions lifted, then it will have to prove that it isn’t deploying the system. To do this, a monitoring system is one way to make the case that Turkey is trying. Washington can reward such a change in policy, perhaps through the lifting of blocks on Foreign Military Sales. Such a move would free up Turkey to service its aging F-16s, and do so in a way that doesn’t involve the SSB because the agreement would be made directly with the Turkish military. This approach would forestall any Turkish need to purchase Russian jets, as an interim measure to replace or augment aging air frames.

The ball is now in Ankara’s court. The Turks have no shortage of ways they could respond to U.S. sanctions, but to reset relations with President-elect Biden, Ankara will have to consider how it intends to signal that it is ready to compromise. This transactional approach to foreign policy is exactly what Turkish officials have claimed they wanted; however, it requires that Ankara offer something to Washington as part of a mutually beneficial exchange. Ankara can offer not to deploy the system and allow Washington to verify that transaction in exchange for a pathway to the removal of sanctions. Ankara could, of course, choose to double down on its current policy and seek more arms from Russia. That is the decision Ankara now has to make, and the bilateral relationship now depends on Turkey’s next move.

The views expressed in this article are those of the authors alone and do not necessarily reflect the position of the Foreign Policy Research Institute, a non-partisan organization that seeks to publish well-argued, policy-oriented articles on American foreign policy and national security priorities.