For the second time in less than a month, US warplanes have carried out an attack on pro-government forces in Syria, attacking Shi’ite militia forces in the nation’s south, accusing them of having crossed into the “safe zone” area around Daraa.

The Syrian government condemned the attack, saying it proved the US was “in support of terrorism” in carrying out the attack. Syrian forces in and around Daraa have recently been fighting against al-Qaeda’s Nusra Front, in particular, and elsewhere in the south are also trying to soften up ISIS forces near Palmyra.

US officials, however, are presenting the incident as reflective of the “regime” getting too close to Tanf, the southernmost Syrian border crossing into Iraq, and one held by US-backed rebels. Iraqi Shi’ite militias have been moving toward Syria in recent days, and indications are that they intend to establish a land route connecting the militias in Iraq to government territory in Syria to allow them in to fight ISIS. The US sees that as threatening their control over the region, and has warned them against doing so.

The exact toll of the latest US attack is unclear, with Syria saying it “caused deaths and material damage,” while the US only presented it as having destroyed a pair of artillery pieces and an anti-aircraft vehicle, while damaging a tank.