* Turkey opts for Chinese firm under U.S. sanctions
* Commander sees possible NATO role on Syria weapons
* Hopes Afghan security pact will go through unchanged
NATO's top military commander urged Turkey on Wednesday to buy a missile defence system that is compatible with other NATO systems, questioning whether the $3.4 billion Chinese system that Ankara is leaning towards is suitable.
The comments by U.S. Air Force General Philip Breedlove, NATO's Supreme Allied Commander Europe, add to pressure on Ankara to rethink its decision to build a missile defence system with a Chinese firm.
NATO member Turkey said in September it had chosen the FD-2000 missile defence system from China Precision Machinery Import and Export Corp, or CPMIEC, over systems from Russian, U.S. and European firms.
CPMIEC is under U.S. sanctions for violations of the Iran, North Korea and Syria Nonproliferation Act. Turkey later said its decision on the deal was not final.
Stressing that the choice was for Turkey to make, Breedlove said his concern was that all NATO members took decisions that contributed to the collective defence of the alliance and selected equipment that would work with other NATO systems.
"In my conversations with the Turkish military ... the important point is that we have systems that are completely inter-operable and ... suitable for plugging in to NATO networks," he said in an interview with two reporters in Latvia, where he was visiting a major NATO exercise.
Breedlove did not specify what he meant by suitable but some NATO diplomats say plugging Chinese equipment into NATO systems would raise cyber security concerns.
Asked if he hoped Turkey would think again, Breedlove said: "I would sure like to see them buy a completely compatible and suitable NATO capability."
Breedlove said it might be possible to make the Chinese system compatible with NATO systems, but he added: "Can it be made to be suitable to plug into a NATO system? I don't know."
Turkey has asked the United States to extend the pricing on Raytheon Co's Patriot missile defense system proposal, two sources familiar with the discussions told Reuters last week, in a sign that Ankara is keeping its options open in case its talks with CPMIEC fall through.
On Syria, Breedlove held out the possibility that NATO could play a coordinating role in eliminating chemical weapons although no request had been made for it to do so.
Russia and the United States brokered a deal in September to put President Bashar al-Assad's chemical arms stockpiles under international control.
Several NATO member nations had independently offered to help eliminate the chemical weapons stocks, Breedlove said.
But most of those countries wanted to know who would provide transport, who would protect their experts and who would coordinate the operation, he said.
"Several of our nations who are offering (help) are seeking the kind of things that a larger military command-and-control structure would provide, but again at this moment there is no call for ... and no planning for a larger NATO mission," he said.
Breedlove voiced hope that a draft security pact negotiated by the United States and Afghanistan creating a framework for some U.S. troops to stay on in the country after 2014, when combat operations end, would be approved by a "Loya Jirga" of Afghan tribal elders this month without changes.
Agreement on the Afghan-U.S. pact would allow NATO to negotiate a similar agreement with Kabul and permit NATO to finalise its plans for a training and advisory mission for Afghanistan after 2014, he said.