After lengthy negotiations, Turkey and Russia have reached the final stage in talks for the purchase of the S-400 missile defense system. Last week, the final touches on the agreement were put during the Vladimir Putin's visit to Ankara. President Recep Tayyip Erdoğan and the Russian president agreed on principle that the loan would be paid back in installments. According to senior Turkish officials, the only remaining issue is how Turkey will pay for the S-400.

For the Turks, the S-400 missile defense system is really important – mainly due to regional developments. In recent years, a wave of instability and chaos has reached Turkey's eastern and southern borders. Keeping in mind the situation in Syria and Iraq, it is understandable that Ankara seeks to strengthen its air defenses.

To be clear, Turkey's interest in purchasing an air defense system dates back to 2009. At the time, the country identified a number of criteria: technology transfer, joint production and affordable price. In line with those criteria, Ankara's first choice was to work with the United States. However, Washington failed to meet the "technology transfer" and "price" criteria. Similar talks were held with France and China. Although the Turks almost struck a deal with Beijing, the negotiations proved inconclusive in the end.

At the time, the U.S. knew about Turkey's efforts to purchase an air defense system. However, Washington made no effort to reach an agreement with the Turks to jointly set it up. Nor did they try to meet any of Turkey's criteria.

After years of negotiations, Turkey is about to finalize an agreement with Russia. Last week, Foreign Minister Mevlüt Çavuşoğlu repeatedly said that the S-400 deal could be signed anytime. In other words, they are on the final hurdle.

According to sources familiar with the S-400 negotiations, U.S. officials have been sharing their concerns about Turkey's potential cooperation with Russia behind closed doors. Recalling that Turkey was a NATO ally, they reportedly asked Ankara to ensure that its air defense system would be NATO-compatible.

To be clear, the Turks must have taken the same factors into considerations when they initially reached out to the United States. However, Turkey's efforts proved futile. In the end, Ankara started negotiating with Moscow and reached an agreement that served the interests of both countries. Needless to say, the same system continues to be used by other NATO allies, including Greece.

Above all else, there is a question that needs answering: Provided that Turkey isn't an enemy of the United States, why is Washington so opposed to Turkey's efforts to purchase the S-400? To be clear, the Turks have no intention to hurt U.S. interests. Quite the contrary, my sources indicate that Turkey still wants to cooperate with Washington on a range of issues, including the Syrian crisis. As a matter of fact, President Erdoğan himself repeatedly made the same point and even offered to work together on the Raqqa operation.

Time and again, the Americans have turned down Turkey's requests. Moreover, Washington cooperated with the PKK terrorist organization in Syria, which has posed a clear threat to Turkey. To add insult to injury, the U.S. failed to extradite Fetullah Gülen, the mastermind of the July 15 coup attempt. Finally, certain lawsuits have been filed in the United States with the intention of manipulating Turkish politics based on documents smuggled by police officers who have since been dismissed from public service over their links to the Gülenist Terror Group (FETÖ).

In response to Washington's hostile steps, President Erdoğan warned that "we have no plans regarding the United States, but it would appear that the U.S. has a plan against us."

It is possible that U.S. officials don't see Turkey as their country's equal and they might seem not to care about Washington's relationship with the Turks. As a matter of fact, they could be trying to develop a regional policy despite Turkey's objections. Perhaps they think that "the Turks will suffer the consequences if they don't do as we say." All of this is possible. But the U.S. must come to terms with the fact that it won't get results by acting like this.

One thing is clear: Turkey's relations with the United States are at an all-time low. However, it is important to acknowledge that this isn't just Turkey's fault. Clearly, Washington's reckless attitude toward vital threats against Turkey will have a negative impact on the relationship.

If the current process continues, Ankara won't face the consequences alone. The United States, which has been trying to create a new balance of power in the region with the help of Saudi Arabia, the United Arab Emirates, Israel and People's Protection Units (YPG) militants, stands to lose. Unfortunately, Washington is suffering from diplomatic blindness as it sees players with no regional influence as its allies. By contrast, Turkey made significant progress in northern Iraq and Syria by working with other countries. Finally, the fact that the Organisation of Islamic Cooperation (OIC) held an extraordinary summit in Istanbul deserves some credit. Washington must take all of those factors into consideration when it thinks about its relationship with Turkey.

There is still some time before the Americans miss the final exit before the cliff.