US military aircraft have carried out an airstrike on a convoy of pro-Syrian government fighters advancing toward the positions of foreign-backed militants in the south of the Arab country.

AFP quoted unnamed US military officials as saying that the American jets struck a convoy of 27 tanks heading towards a garrison in al-Tanf near the Jordanian border on Thursday.

"A convoy going down the road didn't respond to numerous ways for it to be warned off from getting too close to coalition forces in al-Tanf," said one of the officials, adding that British and US commandoes have been training anti-Damascus militants at the base in Homs province.

"Then there was finally a strike against the lead portion of” the convoy, which was “significant” in size, the official stated.

There have been no immediate reports on possible casualties as a result of the air raid.

Another US official said the jets carried out “shows of force” in the skies above the tank convoy and fired warning shots before bombing the lead vehicles, which were moving to within 27 kilometers of the garrison.

Reports also said the US-led coalition purportedly fighting militants in Syria unsuccessfully tried to contact Russia to ask the pro-government convoy to stop advancing further south.

In this image released by the US Navy, the guided-missile destroyer USS Porter conducts strike operations against Syria while in the Mediterranean Sea on April 7, 2017.

Citing a source with the US-backed Maghawir al Thawra militant group, Reuters reported that the militants initially clashed with the advancing pro-government forces prior to the airstrike. The report added that at least one tank and a bulldozer were destroyed in the US attack.

Meanwhile, Yehya al-Aridi, a spokesman for the foreign-backed opposition High Negotiations Committee holding talks with a Syrian government delegation in Geneva, “welcomed” the US strike as a “robust action” against pro-government fighters in the war-torn country.

The development comes only a few days after US-led jets killed nearly two dozen civilians in an attack on an area in Syria’s eastern province of Dayr al-Zawr near the border with Iraq.

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In September last year, US-led coalition airstrikes on Syrian army positions near Dayr al-Zawr military airport also killed over 80 soldiers.

Russia called an emergency United Nations Security Council meeting over the attack, which was conducted by two F-16 and two A-10 jets that had entered Syrian airspace from Iraq.