On several occasions in recent weeks, warplanes of the US -led coalition have also struck pro-government forces to prevent them advancing from the Al Tanf garrison in southeastern Syria at a spot where the country's borders join Iraq and Jordan.
And on Monday, a USA fighter jet shot down a pro-Syrian regime drone in southeastern Syria.
The coalition statement said the location was close to where another "pro-regime" drone - which intelligence sources had also identified as Iranian - was shot down on June 8 after dropping bombs near coalition forces.
Coalition forces are using the Al-Tanaf base by Syria's borders with Jordan and Iraq to train anti-jihadist Syrian fighters and stage attacks against IS.
"The Coalition does not seek to fight Syrian regime, Russian, or pro-regime forces partnered with them, but will not hesitate to defend Coalition or partner forces from any threat".
The more dramatic response seemed to come from Russia's Defense Ministry, which issued threats of a kinetic response against USA jets west of the Euphrates in Syria, referring to them as "air targets". The ministry also said that Russian Federation was discontinuing cooperation with the U.S. military as part of the memorandum on preventing mid-air incidents and ensuring flights safety during operations in Syria. It marks the second time that forces supporting the Syrian government have attacked or tracked inside a so-called "deconfliction" zone near At Tanf, close to the Jordanian border.
The deconfliction line between the two countries had first been suspended by Russian Federation in April after the United States launched a missile strike on a Syrian military airfield. Today, the coalition announced that it had shot down an armed UAV that was headed towards coalition positions near the us base at al-Tanf.
Murphy's remarks came two days after a U.S. Navy fighter jet shot down a Syrian warplane for the first time, prompting Russian Federation to issue a threat against American airborne assets over Syrian airspace.
The newly elected Liberal government withdrew the CF-18s the following year, but kept the other planes in the region to continue supporting fighter jets from the USA and other allied countries.
The U.S. military meanwhile confirmed Tuesday that top IS cleric Turki al-Binali was killed in a coalition airstrike on May 31, in Mayadeen, Syria.
Elsewhere, government air and artillery bombardments hit rebel-held areas of the Syrian city of Deraa after a two-day ceasefire expired, the Syrian Observatory for Human Rights said. The 48-hour truce that had started there at noon Saturday was supposed to be extended.
"The situation is back as it was in Daraa city and fighting is ongoing", said Daraa-based opposition activist Ahmad al-Masalmeh.
"Stating that coalition aircraft within a certain region of the country will be "tracked" could be read as anything from just monitoring their movements, which Russian Federation will be doing anyway, up to far more hostile measures like locking on with fire control radars".
The U.S. entered Syria in September 2014 after ISIS swept into Iraq and Syria and threatened to topple Baghdad and gain more territory from the embattled Syrian regime, which had been fighting a civil war since 2011.
In another first, Iran fired ballistic missiles at Islamic State targets in eastern Syria, in the province of Deir el-Zour, later on Sunday.