German Chancellor Angela Merkel arrived in Turkish southern Gaziantep province Sunday for a two- day visit to boost bilateral relations. This is Merkel's third visit to Turkey since she became German chancellor. Merkel will first go to Turkey's southern province of Kahramanmaras near the border with Syria, where Patriot missile systems sent by Germany were installed. She will then proceed to central Anatolian province of Nevsehir. Merkel will tour Goreme National Park Monday morning, and then proceed to the Turkish capital of Ankara at noon. On Saturday, German Defense Minister Thomas de Maiziere, together with Dutch Defense Minister Jeanine Hennis-Plasschaert and Turkish Defense Minister Ismet Yilmaz, inspected Patriot missile batteries close to the Syria-Turkey border, saying they delivered a "clear warning" to Damascus that NATO would not tolerate missiles fired into Turkey. One day before her trip, Merkel said in her regular weekly video message that she was sceptical about Turkey's European Union (EU) membership bid, but she favored opening discussions in a new policy area or "chapter" with Ankara to bring fresh momentum. "I think a long negotiating path lies ahead of us. Although I am sceptical, I agreed with the continuation of membership discussions. We are engaging in these with an open result," Merkel said. Turkey's efforts to join the EU have been stalled in recent years, and of the 35 so-called policy chapters EU candidates must negotiate, Turkey has opened talks on only 13 since it formally applied for membership in 2005. Trade volume between Turkey and Germany stood at 34.5 billion U. S. dollars in 2012. Over 5,000 German companies have invested in Turkey with a strong presence in car-manufacturing industry. The ties between the two countries were shaken in 2011 when a terrorist neo-Nazi ring was discovered to be behind the killing of eight Turkish citizens and one Greek citizen between 2000 and 2007.