Turkey has invited Russian, U.S. and Chinese companies to submit proposals for this system which would expand on their older NATO legacy systems. The fact that they are looking outside of their NATO allies for such a system says volumes about how integrated their defense and foriegn policy is with that alliance.
President Obama has moved the focus of missile defense in Europe from a large fixed system to one based on ships and mobile ground systems. If Turkey did buy the U.S. PATRIOT or THAAD systems like many countries have it would be easier to integrate it into a unified missile defense for threats coming from the south or east.
The other motivation for these countries is that the contract would be good business for their defense contractors. The motivation to sell systems overseas is that it reduces the total cost of each unit making them cheaper for the original developer. These sales also help mitigate industrial base issues as they keep a production line hot longer. In some cases this motivates the seller to provide the systems at a loss just to benefit from keeping the company going.
Congress has approved the sale of the PATRIOT to Turkey but the final deal won't be awarded until 2010. This would help Raytheon (RTN) and Lockheed Martin (LMT) as they are the producers of this system. There is also the chance that the Russian or Chinese system could be purchased instead. Turkey has traditionally bought U.S. weapons and over the last ten years has invested in modern F-16 aircraft as well as tankers and airborne radar systems and plans to buy the F-35 JSF. It also has invested heavily in developing its own arms industry through deals allowing it to assemble foriegn weapons and make parts.
It can be assumed that if Turkey does go ahead with this deal that the same kind of arrangement will be set up. This will provide Turkey with a capability few nations possess to at least manufacture advanced rocket motors, guidance systems and warheads along with powerful radars and data links. These are all capabilities that may transfer into other systems including offensive ones. The U.S. must make sure that Turkey intends to stay close to them and the West if this kind of deal goes through.