"However, the United States will not hesitate to use necessary and proportionate force to defend USA, coalition or partner forces, as we have clearly demonstrated in past instances", CNN quoted Pentagon spokesman Cmdr.
At Tanf is a key USA stronghold near the border of Syria, Jordan and Iraq, used to root out militant troops in the area, as U.S.
The US has always been fine with Islamists on the Jordan border, and is warning Russian Federation against taking any action against them, saying the US would view it as a "challenge" and that they would not hesitate to respond militarily if there is any move into the area. Earlier this year, though, USA forces bombed and killed a couple hundred Russian mercenaries when they crossed a deconfliction zone in Deir el-Zour.
More than 100 USA troops began conducting live-fire exercises near a US base in southern Syria following Russian threats on the area.
"Our forces will demonstrate the capability to deploy rapidly, assault a target with integrated air and ground forces, and conduct a rapid exfiltration anywhere in the OIR combined joint operations area", stated US Navy Capt. Bill Urban, the spokesman for CENTCOM.
Another of the admitted objectives of the us presence at al-Tanf is to recapture the strategic border crossing of Abu Kamal, which is under Syrian government control. Tensions were raised in February after dozens of Russian mercenaries were killed during a failed assault on a US-held position near the city of Deir al-Zor.
US officials who work on the Syria issue have said in recent days that the administration is now resolved to stay in Syria longer than President Trump previously indicated, to finish the fight against Islamic State but also to see the withdrawal of Iranian fighters.
On Saturday, the Russian Defense Ministry claimed to have captured a group of militants who said they had a training camp near the American military base in At Tanf.
The drills come just one day after Russian Federation accused coalition forces of harboring terrorists in the area and threatened to conduct operations and launch precision strikes around a key anti-ISIS coalition base in At Tanf.
The US reportedly warned Russian Federation that it would defend itself if attacked.
"We have absolutely advised them to stay out of At Tanf", one U.S. official said.
"The U.S. does not require any assistance in our efforts to destroy [Islamic State] in the At Tanf deconflicition zone, and we advised the Russians to remain clear", Brown said.
Also Friday, at the United Nations, the Syrian ambassador, Bashar Jaafari, declared his government was determined to move on rebel-held Idlib to wipe out what he called factions associated with "terrorist groups".
The exercise comes after Russian Federation reportedly warned the United States that it and its Syrian regime allies are prepared to launch an attack near the base.
On Monday, Trump took to Twitter to warn Syrian president Bashar al-Assad not to "recklessly attack" Idlib province.