The US-led coalition fighting ISIS in Syria launched its third strike in as many weeks on pro-regime forces inside a deconfliction zone around al Tanf, near a border crossing in Syria's southeast desert.
Two US officials told CNN that Thursday's strike came after three vehicles were seen entering the deconfliction zone, and two of the vehicles were hit when they were 24 miles from the base at al Tanf.
Following that engagement, a US aircraft downed a pro-regime drone that was dropping bombs near coalition troops.
"The pro-regime UAV, similar in size to a U.S. MQ-1 Predator, was shot down by a U.S. aircraft after it dropped one of several weapons it was carrying near a position occupied by Coalition personnel who are training and advising partner ground forces in the fight against ISIS," US Central Command said in a statement.
The "munition did not have an effect on coalition forces,"according to coalition spokesman Col. Ryan Dillon.
US and other coalition personnel are at the al Tanf garrison, near the border crossing, to train local partner forces, who captured the area earlier this year. (US personnel and local partners repulsed an intense attack by ISIS soon after.)
The first such strike in the al Tanf area came on May 18, when coalition forces targeted pro-Assad forces "that were advancing well inside an established de-confliction zone" spreading 34 miles around al Tanf, US Central Commandsaid in a release at the time.
The strike came after unsuccessful Russian efforts to stop the movements, a show of force by coalition aircraft, and warning shots.
Earlier this week, pro-regime and coalition aircraft both conducted strikes against opposition forces in the vicinity of al Tanf.
On Tuesday, Iranian-backed Shia militia fighters came under attack on the ground just inside the deconfliction zone boundary, according to CNN. In response to that attack, Washington and Moscow communicated on a deconfliction line set up previously. Russia shared a request from the Syrian government to launch a strike in support of the militia, to which the US agreed.
Hours later, pro-Assad forces were observed entering the deconfliction zone with vehicles and weaponry, including a tank and artillery, as well as over 60 fighters. The US then launched its own airstrike on those forces after they refused to withdraw from the area.
The coalition said it issued several warnings before "destroying two artillery pieces, an anti-aircraft weapon, and damaging a tank."
The US-led strike, carried out by a F/A-18 fighter, dropped four bombs and "killed an estimated 10 fighters,"according to CNN.
Thursday's engagements add to a string of encounters that could lead to greater conflict in Syria between the US-led coalition and its local partners and pro-regime forces and their backers, Iran and Russia.
"The Coalition does not seek to fight Syrian regime, Russian or pro-regime forces partnered with them," CentCom said in its statement on Thursday.
"The demonstrated hostile intent and actions of pro-regime forces near Coalition and partner forces in southern Syria, however, continue to concern us and the Coalition will take appropriate measures to protect our forces," the statement said.
The strategic value of the al Tanf area — through which a highway connecting Damascus to Baghdad runs — as well as the direction of events elsewhere in Syria makes clashes between coalition forces and pro-regime forces a continuing possibility.
ISIS' eroding control of territory in Syria, and the likelihood that Kurdish forces — who've signaled a willingness to negotiate with Assad for autonomy — will soon take control of the area around Raqqa in northeast Syria make territory in the southeast of the country increasingly valuable.
Recent events in Syria indicate that "the United States [is] seemingly looking to cement a north-south 'Sunni axis' from the Gulf states and Jordan to Turkey," Fabrice Balanche, a French expert on Syria and a visiting fellow at The Washington institute for Near East Policy, wrote recently.
"The challenge is that Iran and its proxies would very much like to establish some sort of land bridge from Iraq into Syria and they have had designs on this for quite some time,” a former Pentagon official told The Christian Science Monitor.
Capturing al Tanf and the nearby border crossing would allow Tehran to link Iraq to the Mediterranean coast through Syria, facilitating the movement of men and material.
But doing so would also isolate coalition-backed forces fighting ISIS and their special-forces advisers.
Intelligence sources have told Reuters that the coalition's presence near al Tanf is meant to prevent such a route from opening.
"Initially, the United States and the coalition had planned this unconventional warfare campaign to pressure the middle Euphrates River valley and cut off [ISIS communications lines]," the former Pentagon official said. "Now, ironically, it’s not just threatening [ISIS], it's also threatening Iran's designs for the area."
Russia has also become involved in the confrontations around al Tanf.
Earlier this month, coalition-backed Syrian forces attacked Shia militias that had moved down the highway toward the Iraqi border. They forced the militias, which are backed by Iran, to retreat, but Russian jets soon launched strikes against the coalition-backed fighters, forcing them back as well.
Hezbollah, a Lebanon-based Shia militant group backed by Iran and heavily involved in the pro-regime fight in Syria, has entered the fray as well. The group's military-news unit issued a statement this week warning that the "self-restraint" it had about US-led airstrikes would end if the US crossed "red lines."
"America knows well that the blood of the sons of Syria, the Syrian Arab Army, and its allies is not cheap, and the capacity to strike their positions in Syria, and their surroundings, is available when circumstances will it," the statement said.
Observers have noted that the Trump administration would likely be much less hesitant about attacking Hezbollah in Syria. Given the web of alliances that now ensnare forces in Syria, such attacks would likely have broader repercussions.
"American unwillingness to confront Iran and its proxies in Syria, if obliged by circumstances, is a thing of the past," Frederic Hof, director of the Atlantic Council's Rafik Hariri Center for the Middle East and a former State Department liaison to Syrian opposition forces, told The Christian Science Monitor.
"And Moscow would now have to anticipate with high likelihood aerial combat with US forces should it elect to provide tactical air support to Iran and its proxies on the ground," Hof added.
“Our people are gathering in the Tanf area right now, so a clash is definitely coming,” a Hezbollah unit commander in Beirut, speaking on condition of anonymity, told The Monitor.
SEE ALSO: The US-led coalition destroyed more pro-Assad forces at a growing hotspot in the Syrian desert
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