US troops and Russia-backed Syrian forces set to come into contact as they close in separately on Isis

There are considerable tensions between the two forces opposing the jihadists with fears of an escalation in conflict in the crowded battlefield

US-backed Syrian Democratic Forces, pictured, are set to come into contact with Russian-backed Syrian government forces in the crowded war to drive out Isis (Reuters)

US-backed forces and Syrian government troops, supported by Russia and Iran, look set to come into contact as they each make separate advances against Isis in Syria.

The Syrian Democratic Forces (SDF) launched an offensive against Isis along the border with Iraq on Saturday, bringing them into a race with government forces marching in the same direction against the extremists.

The duelling battles for Deir Ezzor highlight the importance of the oil-rich eastern province, which has become the latest focus of the international war against tIsis, raising concerns of an eventual clash between the two sides.

The US-trained Deir Ezzor Military Council said it was calling its operation Jazeera Storm, after the familiar name for northeast Syria. The Military Council is a part of the predominantly-Kurdish SDF which enjoys broad U.S. military support. The SDF are the US's primary ally in the fight against Isis in Syria.

The race to reach the Iraqi border will shape future regional dynamics, determining whether the United States or Russia and Iran will have more influence in the strategic area once the extremist group is defeated.

Iran has been one of President Bashar al-Assad's strongest backers since the crisis began in March 2011 and has sent thousands of Iranian-backed fighters and advisers to fight against insurgent groups trying to remove him from power.

The US-backed fighters are up against a huge challenge to reach Deir Ezzor, especially while they are still fighting to liberate Raqqa from Isis. Three months into the battle, they have liberated around 60 per cent of the city, and much more difficult urban fighting still lies ahead.

This week, Syrian troops and their Iranian-backed allies reached Deir Ezzor, breaking a nearly three-year-old Isis siege on government-held parts of the city in a major breakthrough in their offensive against Isis. In a victory statement, the Syrian military said Deir el-Zour will be used as a launching pad to liberate the remaining Isis-held areas along the border with Iraq.

The Syrian conflict began with a popular uprising against Assad in 2011, which was initially viewed by the western world as heralding a positive new dawn for democracy in the Middle East.

The subsequent chaos has drawn in the US, Russia and regional powers with peace talks failing to resolve a war.

“The first step is to free the eastern bank of the Euphrates and the areas Isis still holds,” Ahmed Abu Kholeh, head of the Deir Ezzor Military Council, told Reuters after the announcement of their offensive.

“We’re not specifying a timeframe but we hope it will be a quick operation,” he said at the town of al-Shadadi in Hasaka province, adding that he did not know where the battle would move on to once that objective has been achieved.

He said SDF fighters did not expect clashes with Syrian government forces, but if fired upon “we will respond”.

The Syrian Observatory for Human Rights monitoring group reported that SDF forces had advanced against Isis in Deir Ezzor's northwestern countryside, seizing several hilltops and a village.

Meanwhile, Syrian government forces and their allies reached Deir Ezzor military airport on the other side of the Euphrates, where troops had been holed up since 2014, surrounded by Isis, the commander in the pro-Assad alliance said.

The alliance includes Iran-backed militias and the powerful Lebanese Shia group Hezbollah.

The advance came days after the army and its allies broke the siege of the main part of the city, which had been separated from the airport by Isis attacks a few months before.

Syrian troops have now recaptured an oilfield southwest of Deir Ezzor and seized part of a main highway running downstream to the city of al-Mayadeen, to which many Isis militants have retreated, the British-based Observatory said.

Isis fighters in Syria still control much of Deir Ezzor province and half the city, as well some territory further west near Homs and Hama, where government forces recaptured several villages on Saturday, pro-Damascus media reported.

But the group has lost most of its caliphate which from 2014 stretched across swathes of Syria and Iraq, including oil-rich Deir Ezzor.

The SDF is still battling to eliminate Isis from the final areas it controls in Raqqa, northwest of Deir Ezzor.

Talks between Russia, Iran and opposition backer Turkey in the Kazakh capital Astana are set to take place next week, possibly followed by a separate track at the United Nations in Geneva in October or November.

Assad’s government has participated in previous rounds from a position of power as Damascus clawed back much territory, including the main urban centres in the west of the country and increasingly in eastern desert held by the jihasists.

Syria’s non-Islamist opposition holds some pockets of territory in western Syria, and the SDF, which is dominated by the Kurdish YPG militia, controls much of Syria’s northeast.

In June, after the SDF shot down a Syrian government fighter plane, the Syrian army called this a “flagrant attack" and "an attempt to undermine the efforts of the army as the only effective force capable with its allies ... in fighting terrorism across its territory.

“This comes at a time when the Syrian army and its allies were making clear advances in fighting the Daesh (Isis) terrorist group,” it added.

Additional reporting by Reuters