BEIRUT — Turkey achieved a milestone in its goals in Syria: It established a foothold in the heart of the country’s north after driving Islamic State militants away from its borders and seizing al-Bab, one of the extremist group’s major strongholds and a major supply route. But Turkey’s determination to also push back the Kurds is alienating the other big players in Syria — Russia and the United States — and threatens to undermine the fight against IS in the imminent assault on Raqqa. Ankara’s threats to attack the nearby town of Manbij, held by U.S.-backed Kurdish-led forces, prompted Washington to deploy new troops in the area to prevent Turkish advances. Turkey’s Syrian allies have been fighting the Kurds around the town, reportedly with Turkish cover, raising the possibility of frictions with the Americans. At the same time, Turkish forces shelling Kurds hit Syrian government forces, whose patron Moscow reportedly has advisers in the area. As a result, Ankara has effectively unified Russia and the U.S. in the goal of limiting Turkish expansion in the north. Syria experts say Ankara has lost influence to realize its aim of pushing the Kurdish forces back to the east of Manbij across the Euphrates. Moreover, Washington is pushing ahead with partnering with the Kurdish-led forces in the planned attack on Raqqa, despite Turkish opposition. “Turkey’s valuable leverage” to disrupt that alliance “has been tossed away as the Russian military and U.S. Special Forces moved last week in Syria’s Manbij to prevent Turkish-backed Syrian opposition forces from attacking the city,” wrote Ragip Soylu, a Washington-based Turkish columnist for the pro-government English language Daily Sabah newspaper. From the start, Turkey’s goal with its military incursion into Syria has been to push IS militants back from its border and prevent Kurdish forces from holding contiguous territory from east to west across the border. Turkey considers the main Syrian Kurdish force, the People’s Protection Forces, or YPG, as terrorists since they are linked to Kurdish insurgents in Turkey. Capturing al-Bab last month met both those aims. Turkish forces and allied Syrian fighters marched into al-Bab after the militants withdrew following a grueling fight that lasted over two months and claimed dozens of Turkish soldiers. With al-Bab in its hands, Turkey blocked the Kurds from joining territory they hold to the east and the west. But from the very start, a chief goal was Manbij, a small but crowded town 40 kilometers east of al-Bab that is the birthplace of one of the Arab world’s most prominent classical poets. When the U.S-backed, Kurdish-led Syrian Democratic Forces captured the town from IS in August, Turkey sent its troops into Syria, complaining to the Americans that the Kurdish forces must retreat east across the Euphrates. “Turkey has always set the Euphrates as a red line,” Noah Bonsey, an analyst with the International Crisis Group, said in a telephone interview. “The problem is it will be a huge gamble to really do that with US, Russia and YPG, who are a proficient fighting force.” In a new move, U.S. military moved in with small number of troops now positioned on the western outskirts of Manbij to prevent an escalation of violence between its two allies. Calling it a mission to “reassure and deter,” U.S. officials say the troops, with light combat vehicles and visible American flags, are to keep a lid on the tensions brewing in the increasingly crowded battlefield. U.S. Lt. Gen. Stephen Townsend, of the anti-IS coalition, said all the forces acting in Syria have converged “within hand-grenade range of one another.” “We encourage all forces to remain focused on the counter-ISIS fight and concentrate their efforts on defeating ISIS and not toward other objectives that may cause the coalition to divert energy and resources away from Raqqa,” Townsend said last week. He suggested Turkey has no reason to be in the Manbij area. “With the liberation of al-Bab, Turkey has now secured its border from ISIS.” Meanwhile, as Turkish troops and their Syrian allies advanced east of al-Bab and threatened to move on Manbij, Russia brokered a deal that effectively created a buffer zone between them and Kurdish-led forces by handing over some villages to Syrian government troops. On Thursday, Syrian government media said Turkish shelling killed a number of its troops. Kurdish officials said Turkish advances continued even despite the buffer zone. Ilham Ahmed, a senior official with the Kurdish-led Syrian Democratic Forces, blamed Russia and the United States for emboldening the Turkish push toward Manbij: The U.S. coalition by providing the Turkish forces with air cover during the assault on al-Bab, and Moscow by agreeing to let Turkey take over al-Bab despite a Syrian government push to liberate the town. Now with both U.S. forces and Russian advisers in the area, Turkey is not letting up, she said. “In all the wars the Americans took part in, their forces’ presence has some prestige, status, and confrontations are avoided.” Turkey ultimate intention in pressuring Manbij may be to keep the SDF out of the Raqqa offensive. Ankara has repeatedly demanded to the U.S. that the Kurds not be involved in taking the city, which is the Islamic State group’s de facto capital. Fighting at Manbij ties down SDF fighters that could go to the Raqqa campaign. Ahmed said if the U.S. wants the Raqqa campaign to move ahead, “they must protect Manbij.” “All of this is a reminder of the risk in a rushed attempt to get to Raqqa If Turkish interests are not at least placated to some extent,” said Bonsey of the International Crisis Group. Turkey has a number of ways it could disrupt a Raqqa campaign, he said. “There is a lot that can go wrong.” Copyright 2017 The Associated Press. All rights reserved. This material may not be published, broadcast, rewritten or redistributed.