The U.S. military carried out an air strike on Thursday against militia supported by the Syrian government that posed a threat to U.S. and U.S.-backed Syrian fighters in the country's south, U.S. officials told Reuters on Thursday.
The militia, who numbered in the dozens and drove a tank and a small number of construction vehicles, ignored warning shots from U.S. aircraft and, according to a U.S.-led coalition statement, even "apparent Russian attempts to dissuade" their advance.
One of the U.S. officials, who spoke on condition of anonymity, speculated that the group might have been trying to establish a position near the garrison in Syria used by U.S. and U.S.-backed forces around the town of At Tanf.
A member of the U.S.-backed Syrian rebel forces told Reuters the convoy comprised Syrian and Iranian-backed militias and was headed toward the Tanf base when they clashed with some rebel forces.
The militia were struck after they had advanced to about 17 miles (27 km) from the base.
"We notified the coalition that we were being attacked by the Syrian army and Iranians in this point, and the coalition came and destroyed the advancing convoy," said Muzahem al Saloum of the Maghawir al Thwra group.
But the latest move showed that the area around the Tanf garrison in southern Syria could be under pressure.
Tanf is part of a region known as the Badia, which consists of vast, sparsely populated desert territory that stretches all the way to the Jordanian and Iraqi borders and was declared a military priority by Syria's foreign minister earlier in May.
Two months of U.S.-backed rebel advances against Islamic State militants have allowed them to secure swaths of territory in the Badia, alarming the Syrian government and its allies.
But rebel sources had warned last week that the Syrian army and Iranian-backed militia moved hundreds of troops with tanks to the town of Sabaa Biyar, which is in the Badia, and is near the strategic Damascus-Baghdad highway.
A Western intelligence official, speaking on condition of anonymity, said the strike sent a strong message to Iranian-backed militias that have been spearheading the advance that they would not be allowed to reach the Iraq border from Syria.
The U.S.-led coalition did not signal it would cede ground around Tanf.
American airstrikes targeted a group of Syrian militia vehicles after they ignored U.S. warnings and violated a “de-confliction zone” on Thursday.
Route 90, which connects Eilat to the rest of the country was shut in both directions from the Arava junction. Route 12, to the west, was also closed.
The Environment Ministry cautioned that those at risk, including children, the elderly, the ill, and pregnant women, should refrain from going outside, while the general population should not take part in strenuous physical activities outside.
Sandstorms often accompany hot winds blowing in from the Sinai desert.