UPD: The Hezbollah media wing and the Russian Defense Ministry confirmed the reports.
The Syrian Arab Army and its allies have reached the Iraqi border northeast of the village of at-Tanf controlled by special oeprations forces of the US-led coalition member states and Western-backed militant groups, according to Elijah J. Magnier, a chief international correspondent of the al-Rai media outlet.
— Elijah J. Magnier (@EjmAlrai) 9 June 2017
According to Elijah J. Magnier, pro-government forces reached the border in the area just few km from at-Tanf. The Popular Mobilization Units (described by the mainstream media as pro-Iranian proxies) control the same area from the Iraqi side.
If reports are confirmed and government forces are going to set up positions in the area, the US-led coalition and its proxies will likely use a force to drive the Syrian government forces back from the border with Iraq.