AMMAN, Jordan — Forces battling the Islamic State (IS) in Syria seem to be putting a lot of effort into thwarting each other's strategies.

Syrian government troops, backed by allied Iraqi and Iranian militias, are bolstering their control along parts of the Syrian-Iraqi borders. Leaders of the Syrian armed opposition factions who spoke with Al-Monitor confirmed earlier reports that the Syrian government aims to create a land passageway from Iran though Iraq to Syria, to reach Syria's oil-rich Deir ez-Zor, which has been under IS control since 2014.

The leader of Jaish Usud al-Sharqiya, a faction backed by the US-led coalition, accused the United States of “disappointing the rebels and not backing them enough to be able to tighten their grip on the areas" in the Syrian desert they had cleared of IS. Leader Talas Salama (also known as Abu Faisal) told Al-Monitor, “We liberated Rif Dimashq, the eastern part of Suwayda, Daraa countryside and the Damascus-Baghdad highway. But the regime [took] control of the areas that IS was expelled from.”

According to Syrian Central Military Media, which is affiliated with the Syrian regime, the Syrian army and its allies took over the Baghdad-Jordan-Damascus triangle in the Syrian desert on May 12 after defeating Syrian opposition factions. The army's forces also tightened the noose on the Zaza triangle and the town of Sabaa Biyar, which also were under the opposition’s control.