After making significant territorial gains in western Mosul and reaching the Syrian border, Iran-backed Iraqi militia forces today announced that they plan to “recapture” the strategic al-Tanf border crossing from the U.S.-backed Syrian opposition groups, the . They added that they will coordinate their operation with the Syrian Army and seek its help. “The Syrian Desert to the direction of the country’s south will witness extensive clashes between forces supported by Damascus and terrorists over the control of the al-Tanf border crossing,” wrote Fars News Agency, which is affiliated with the Islamic Revolution Guards Corps (I.R.G.C.). According to I.R.G.C. and Iraqi media outlets, the units of the Popular Mobilization Forces (P.M.F.) that will launch the al-Tanf operation are Kata'ib al-Imam Ali, Kata'ib Abu al-Fadhal a-Abbas, and the Kata'ib Hezbollah (also known as the Iraqi Hezbollah).

Fars News Agency added that the pro-Damascus militia forces will use a different route to reach al-Tanf – mainly passing through regions controlled by the Syrian Army. “The terrorist groups - Jaysh Maghawir al-Thawra (the Revolutionary Commando Army) and Usud al-Sharqiya (the Lions of the East Army) – are attempting to prevent the Iraqi groups from advancing toward the administrative borders of the al-Tanf crossing. As a result, these [Iraqi] forces have changed their route to the north to reach the crossing through the Uqda al-Zarqa region.”

Comment: The buildup of Iran-supported militias close to the U.S.-controlled de-confliction zone in the al-Tanf region signals escalating tension between Tehran and Washington over the Syrian conflict. On May 18, the U.S. military for the first time targeted an Iranian-directed convoy in southern Syria after it ignored warnings and continued to approach the de-confliction zone, where the U.S. military is training Syrian opposition forces to fight the Islamic State.

The air strike was meant to send a strong signal to the Iranian-supported forces that they will not be allowed to reach the Iraqi border. But as today’s reports in the Iranian media indicate, the I.R.G.C. and its proxy groups in Syria are still determined to challenge the presence of the U.S. military forces along Syria’s borders with Jordan and Iraq. This is despite the fact that a U.S. aircraft dropped leaflets around the Tanf region over the weekend to warn pro-Damascus militias not to advance toward the de-confliction zone, and U.S. military officials the buildup of Iran-supported forces near al-Tanf as a “direct threat” to coalition forces. This raises the likelihood of more direct confrontation between Iran-controlled forces and the U.S. military and its allies in the region.

While the Iranian-controlled militias do not have the capability to seize the al-Tanf border crossing, they may try to prevent U.S.-backed Syrian opposition groups from expanding their control in southeastern Syria.

The I.R.G.C. media claims that the U.S. military has beefed up its presence in border regions in southern and eastern Syria in order to block the Iranian-supported forces to link the land routes between Syria and Iraq. But an even bigger concern for the I.R.G.C. appears to be U.S. support for anti-regime Syrian opposition groups in southeastern Syria. Reports and commentary in the Iranian media shows that Tehran believes that Washington and its allies have a broader plan to train and equip rebel groups to reverse the latest territorial gains of the Bashar al-Assad regime and its foreign allies under the pretext of fighting the Islamic State.

Parallel to efforts in Syria, I.R.G.C.-controlled Shiite militia groups have made significant territorial gains in Iraq. Iran-backed Iraqi paramilitary groups control strategic regions in western Mosul and recently reached the Syrian border.