Russian President Vladimir Putin and Turkeys Recep Tayyip Erdogan hoped on Tuesday to cooperate together to ease tensions in Syria’s Idlib province. Meeting for talks near Moscow, they expressed deep concerns over fighting in the northwestern region, with Ankara warning it would take the steps necessary to protect its troops there. Russian-backed regime forces launched a ground offensive this month against Idlib, one of the last major areas of Syria outside regime hands. The fighting is threatening to increase tensions between Russia and Iran, who back Bashar Assads regime, and Turkey which supports some opposition groups. "The situation in the Idlib de-escalation zone is of serious concern to us and our Turkish partners," Putin said at a press conference with Erdogan carried on Russian state television. He said Turkey had "legitimate interests" to protect on its southern borders and supported the creation of a security zone in the area. Putin said he and Erdogan had agreed "additional joint steps" to "normalize" the situation in Idlib, but did not provide details. Moscow and Ankara last year struck a deal to create a "de-escalation" buffer zone around Idlib to avert a full-scale regime assault. But Assads forces have been bombarding the province for months and on August 8 launched a ground offensive. Turkey established 12 military observation posts in Idlib under the buffer zone deal and one of them has been encircled by regime forces. "The situation (in Idlib) has become so complicated that at this moment our troops are in danger," Erdogan said. "We do not want this to continue. All necessary steps will be taken here as needed." He stated it was unacceptable that Syrian forces were “raining death on civilians from the air and land under the pretense of battling terrorism”. He also said Turkey had the right to self-defense on its border. “I conveyed our country’s determination on this matter personally to my dear friend Mr. Putin,” Erdogan added. Tuesdays talks between Putin and Erdogan came ahead of a summit on Syria that will see the two leaders joined by Irans President Hassan Rouhani in Ankara on September 16. Erdogan said the September meeting "should contribute to peace in the region". Both leaders said they supported Syrias territorial integrity, but Putin emphasized the need to keep fighting extremist forces in Idlib. "The de-escalation zone must not serve as a refuge for militants, let alone a bridgehead for new attacks,” Putin said. Idlib is dominated by extremist group Hayat Tahrir al-Sham, the former Al-Qaeda affiliate in Syria. Recent fighting has been fierce in the province, the last major front in a war that has killed more than 370,000 people and displaced millions since 2011. Putin and Erdogan met on the sidelines of the MAKS international air show on the outskirts of Moscow -- a showcase for Russias military and civil aerospace industry. The two leaders highlighted their increased cooperation, which saw Turkey begin taking delivery in July of Russian S-400 missile systems it ordered in defiance of warnings from Washington. Turkeys defense ministry said the second stage of deliveries had begun on Tuesday and would last for a month. Putin said he and Erdogan had discussed further military cooperation, including on Russias Sukhoi Su-35 fighter jet. A move by NATO member Turkey to purchase Russian fighters would be sure to further anger Washington. "We have many opportunities, we demonstrated new weapons systems and new electronic warfare systems," Putin said. "In my opinion there was a lot of interest from our Turkish partners."