AMMAN: As US-backed rebels confront the Islamic State in Syria’s strategic eastern desert, regime forces are capturing chunks of their rear positions farther west, with opposition sources telling Syria Direct that the American-led coalition is “not our partner” in the fight against President Bashar al-Assad.

The Assad regime and its allies captured more than 100sq km from both Islamic State militants and rebel forces over the weekend in the Syrian Badia, a sparsely populated desert region spanning the country’s southern border with Jordan and Iraq. For the first time since 2015, Assad took control over the country’s largest phosphate mines as well as the primary highway linking Palmyra to Damascus. The turf battles come as both regime and rebel fighters race to carve out territory left behind by an Islamic State (IS) in retreat.

As opposition forces battled IS fighters farther east over the weekend, pro-regime soldiers attacked the overstretched desert rebels roughly 60km southwest of the ancient city of Palmyra, now firmly under regime control. The regime’s assault led to a swift victory.

The latest advances are the result of the regime “taking advantage” of distracted opposition fighters and “quickly advancing on rebel territory,” a local Free Syrian Army (FSA) field commander told Syria Direct on condition of anonymity on Sunday.

Despite the US-led coalition’s support for rebel forces in the Badia, rebel losses over the weekend highlight a deep misalignment of objectives between the two sides: The coalition wants to focus exclusively on defeating the Islamic State, while rebel fighters want to aggressively confront the Assad regime.

On Monday, rebel sources told Syria Direct that the US-led coalition provides financial and logistical support for opposition forces to combat IS but stops short of funding the rebels to directly attack the regime.

“The coalition is a partner of ours in the war against Daesh [the Islamic State], but when it comes to fighting the regime and its foreign militias, [the coalition] is not our partner,” Al-Baraa Fares, a spokesman for the Free Syrian Army faction Maghawir a-Thawra (MAT), told Syria Direct on Monday.

Russian soldiers clear mines in Palmyra on March 22. Photo courtesy of TASS/Getty Images.

“The role of the international coalition is to train members of MAT and to provide logistical support, weapons, ammunition and all that is needed to eliminate the terrorist Daesh,” he added.

American military forces in the Badia number around 100 soldiers supported by armored vehicles and based out of a small military outpost near the a-Tanf border crossing between Syria and Iraq. Their goal in the Syrian Badia is to push further east, clearing out the Islamic State from along the country’s southern border, entering Deir e-Zor province and ultimately reaching the border city of al-Bukamel, Syria Direct reported.

“Coalition forces have operated for many months training and advising vetted partner forces in the fight against ISIS,” a US military spokesperson with CENTCOM’s Operation Inherent Resolve, told Syria Direct on Sunday via email.

Undeterred by the coalition’s mission objective, the Free Syrian Army announced last Monday a new campaign dubbed “Badia Volcano,” a seemingly independent campaign to “cleanse the Badia of Iranian and foreign militias.”

The MAT brigade says the international coalition will not support its fight against the regime and its allies, spokesman Al-Baraa Fares told Syria Direct. However, “both MAT and the FSA will fight the regime and its militias…and in the coming days, we will have an even larger role in fighting the regime.”

US forces and Maghawir a-Thawra at the a-Tanf border crossing on May 23. Photo courtesy of Hammurabi’s Justice News.

The coalition does, however, maintain a clear defensive perimeter in the Badia beyond which it has stated it will not permit the presence of the regime or its allied forces: a “55km radius around the area in which coalition and partnered forces are operating near a-Tanf,” the US CENTCOM spokesman told Syria Direct in a second email statement on Monday.

“The continued armed and hostile presence of forces inside the de-confliction zone is unacceptable and threatening to Coalition forces,” the CENTCOM spokesman added. “Coalition forces are prepared to defend themselves if pro-regime forces refuse to vacate the de-confliction zone.”

Earlier this month, coalition warplanes attacked a convoy of “tanks, armored vehicles, artillery and technical vehicles” advancing from government-controlled territory towards the outpost, Syria Direct reported.

While the regime has not officially explained its motives behind its recent offensives in southeastern Syria, retaking strategic border areas with Jordan and Iraq could re-establish commerce and ground transportation that stopped years ago due to the war.