"Syria is a major security and geopolitical threat for its all neighbours, beginning with Turkey. Turkey must be at the table in any resolution of this conflict,” said James Jaffrey,  the US envoy for Syria.

 According to Anadolu Agency, James Jeffrey arrived in Turkey on Wednesday with an accompanying delegation to discuss the latest efforts to resolve the now nine-year Syrian conflict.

"We have exciting developments on the Syrian account," Jeffrey told reporters at the airport.

US envoy touched upon Syrian Constitutional Committee's third round of meetings had begun in Geneva.

"It was a good start, much helped by Turkey's encouragement of all members of the Constitutional Committee, particularly the opposition," Jeffrey said.

"The military phase of this conflict needs to end. There is no more ground to be gained by the regime. The regime needs to return to the negotiating table and deal with the rest of the international community. That's our priority," he added.

Referring to Turkish President Recep Tayyip Erdogan's remarks on Tuesday said the US had sided with terrorist organizations instead of its NATO ally Turkey, Jeffrey said that the US is "a close ally of Turkey. We proved our value in many fields outside of Syria."

Reminding the US-Turkey agreement on the cooperation in the north Syria, he said that "we are working to ensure that is maintained. We have very close coordination on Idlib and on the political process and we will continue to do exactly what we're doing."

James Jeffrey will discuss important issues with Turkish officials during his official visit, including the implementation of UN Security Council Resolution 2254 for the resolution of the Syrian conflict, efforts to defeat DAESH\ISIS and the other forms of bilateral cooperation on stability in Syria.

Jeffrey also held talks with Deputy Foreign Minister Sedat Onal in Geneva on Wednesday, as part of the Syrian Constitutional Committee's third round of meetings.

During their meeting, Jeffrey and Onal discussed the political process in Syria, how to support the work of the Constitutional Committee, the situation in Idlib and the maintenance of the cease-fire in the field.

It should be noted that Syria has been mired in a vicious civil war since early 2011, when the Assad regime cracked down on pro-democracy protests.

Hundreds of thousands of people have been killed since and more than 10 million displaced, according to UN figures. Turkey hosts more than 4 million Syrians as the top refugee-hosting country in the world.