Turkey is asking allies including the United States to take part in a joint ground operation in Syria, as a Moscow- backed government advance nears its borders, raising the possibility of direct confrontation between the NATO member and Russia.A large-scale joint ground operation is still unlikely: Washington has ruled out a major offensive. But the request shows how swiftly a Russian-backed advance in recent weeks has transformed a conflict that has drawn in most regional and global powers.“It is not possible for Turkey to accept certain fait accompli happening in the region,” Prof. Mehmet Seyfettin Erol, head of the Center for International Strategy and Security Studies at Gazi University in Ankara told The Jerusalem Post, on Tuesday.Northern Syria and northern Iraq are key areas of importance for Turkish national security and Russia and Iran are threatening this.As the Middle East map is being redrawn it cannot be expected that Turkey would stand still while some states, principally Russia and Iran, are trying to increase their sphere of influence in Syria and Iraq, added the Turkish expert.“Henceforth, Turkey, together with her allies, will play a more active role within the region. Present conditions are forcing Turkey to do so,” added Erol.The offensive, supported by Iranian-backed Shi’ite militias as well as Russian air strikes, has brought the Syrian army to within 25 km. (15 miles) of Turkey’s frontier. Kurdish fighters regarded by Turkey as hostile insurgents have also exploited the collapse of positions held by other rebel groups to seize ground and extend their presence along the border. The advances have increased the risk of a military confrontation between Russia and Turkey.Turkish artillery returned fire into Syria for a fourth straight day on Tuesday, military sources said, targeting the Kurdish YPG militia, which Ankara says is being backed by Moscow.“We want a ground operation.If there is a consensus, Turkey will take part. Without a ground operation it is impossible to stop this war,” a Turkish official told reporters at a briefing in Istanbul.“Turkey is not going to have a unilateral ground operation...We are discussing this with allies,” the official said, declining to be named in order to speak more freely.Prof. Efraim Inbar, a Turkey expert and director of the Begin-Sadat Center for Strategic Studies at Bar-Ilan University, told the Post he doubts whether the Turks will invade Syria and risk a confrontation with Russia, particularly with no American backing.“However, the Turkish government could send commandos and engage in limited air strikes and possibly try to establish a thin Turkish presence in areas not far from their border, particularly in areas inhabited by Turkmen,” added Inbar. For its part, the Russia-led security body, the CSTO, said on Tuesday that heavy artillery bombardment of Syrian targets by Turkey and talks of a ground operation by Ankara and Saudi Arabia risk leading to direct military clashes between regional states.“Further fanning of the conflagration in Syria in close proximity to the zone of responsibility of the Collective Security Treaty Organization is a threat to the security of its member states,” CSTO Secretary- General Nikolay Bordyuzha said in a statement.The CSTO’s members are Russia, Armenia, Belarus, Kazakhstan, Kyrgyzstan and Tajikistan.Turkey has vowed it will not let the Syrian town of Azaz fall into the hands of Kurdish forces because it lies on a supply route used by Ankara to support Islamic State, Russia’s Foreign Ministry said Tuesday.“Some of our partners have literally implored us ‘not to touch’ a corridor that is a bit shorter than 100 km. on the Syrian-Turkish border around Azaz,” Russian Foreign Ministry spokeswoman Maria Zakharova said in official comments, mentioning Washington and its allies also operating in Syria.“Obviously, this is aimed at ensuring continued daily supplies to Islamic State, Jabhat al-Nusra [Nusra Front] and other terrorist groups with weapons, ammunition and food from Turkey via this area, and also to allow it to serve as a passageway for terrorists,” she said.Earlier on Tuesday, the Kremlin strongly rejected accusations by Turkey that Russian bombs hit several medical facilities and schools in northern Syria, saying they were unfounded.Republican People’s Party (CHP) leader Kemal Kilicdaroglu repeated the accusation on Tuesday that the AKP-led Turkish government was aiding jihadist groups in Syria.“Turkey should not lend armed support to jihadist groups in Syria such as ISIL [Islamic State],” he said, the Hurriyet Daily News reported.Meanwhile, a Russian lawmaker said Tuesday that the threat of a Turkish-Saudi invasion of Syria is “an attempt to influence the situation by means of threats and political maneuvers,” Russia’s Tass News Agency reported.“Possible invasion of Syria by Turkey’s land forces is being widely discussed. Naturally, we are keeping a close eye on the steps taken by the Turkish and Saudi leadership,” Alexey Pushkov, the chairman of the international committee at Russia’s State Duma lower parliament house.“It looks like Turkey is making certain military preparations to have such a possibility, and the Russian Defense Ministry is officially speaking about it,” he said.“Riyadh has no troops of its own and it is difficult to say now whether its threats to launch a military invasion of Syria are real or a bluff,” said the Russian lawmaker adding, “Anyway, I don’t think Saudi Arabia can send 100,000 troops, as it said.”Turkey will continue to take preventative measures to avoid becoming involved in the war in Syria, Prime Minister Ahmet Davutoglu said Tuesday.There is an effort to create the impression Turkey is going to war in Syria, but we have kept Turkey out of this war for five years, he said according to Turkish media reports.Davutoglu also criticized Russia’s bombing campaign in Syria as “vile, cruel and barbaric,” Hurriyet reported.Turkey accused Russia on Monday of an “obvious war crime” after missile attacks in northern Syria killed scores of people, and warned the YPG Kurdish militia it would face the “harshest reaction” if it tried to capture Azaz near the Turkish border.Almost 50 civilians were killed when missiles hit at least five medical facilities and two schools in rebel-held areas of Syria on Monday, according to the United Nations, which called the attacks a blatant violation of international law.