The US Congress is set to adopt a law this week forbidding Turkey from using American funds to shop for a US$4 billion missile system in China. The United States has voiced deep concern over Turkey's decision in September to enter negotiations with China Precision Machinery Import-Export Corporation for its first long-range anti-missile system. CPMIEC, which makes the HQ-9 missile system, is under US sanctions for selling arms and missile technology to Iran and Syria. Turkey's move also irritated its allies in Nato, which has said missile systems within the transatlantic military alliance must be compatible with each other. The annual US defence authorisation bill contains a clause barring the use of "2014 funds to integrate missile defence systems of the People's Republic of China into US missile defence systems". "Such a system would not be compatible with, and should not be integrated with, missile defence systems of the North Atlantic Treaty Organisation," the Senate and House Armed Services Committees said. Without American subsidies, the cost for Turkey to install the Chinese missiles becomes steeper. The bill is expected to be approved in the Senate before being signed into law by President Barack Obama. Turkey will make its final decision by next year.