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.
USA officials said it remained uncertain as to who was operating the drones - Whether it was Shiite militia fighters, Syrian officers or Iranian advisers. Neither official could say for sure whether either of the two drones that the US has shot down in southern Syria flew out of that base, but both said it was likely.
The drone was shot down by a U.S. F-15E Strike Eagle aircraft at about 12:30 a.m.
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.
On Sunday, a U.S. Navy F/A-18 warplane shot down a Syrian Air Force Su-22 that had dropped bombs near Syrian opposition forces.
Operations were suspended earlier this week, after a United States fighter jet shot down a Syrian warplane.
In response, Russian Federation announced its air defenses would track all coalition targets west of the Euphrates, and suspend the "deconfliction" hotline. The Russian military department also ceased to cooperate with the U.S. in the framework of the memorandum on the prevention of incidents in the sky over Syria.
The Australian Defence Force said it had been "a precautionary measure to allow the coalition to assess the operational risk".
The U.S. also downed a Syrian government warplane earlier this week in northern Syria.
The U.S. military has repeatedly warned forces fighting on Assad's side to stay away from a "deconfliction zone", agreed with Russian Federation, near a garrison used by U.S. Special Forces and U.S. -backed militia around Al-Tanf, near the border with Jordan.
The United States has taken a series of actions over the past three months demonstrating its willingness to carry out strikes, mostly in self-defense, against Syrian government forces and their backers, including Iran.
The drone was downed just outside the 55 kilometer de-confliction zone, according to the officials.
The defence ministry said Friday that IS fighters have been moving forces into Hama province this week under cover of night and using large buildings there as command points and weapons stores.
The Australian Defense Force is fighting IS in both Syria and Iraq under the name 'Operation OKRA.' Australian Defence Force Chief Mark Binskin said on Wednesday the operations were halted while the Australians examined what was happening in what he had described as a?complex piece of airspace? over Syria.
Officially aimed at IS they were a clear statement to the US.