The Defence Secretary has called on Moscow to respect international airspace after a Russian fighter jet collided with a US surveillance drone, causing the unmanned aircraft to crash-land into the Black Sea on Tuesday.
Speaking to Reuters at the DSEI Japan defence show, Ben Wallace said: "The key here is that all parties respect international air space and we urge the Russians to do so."
The US called it a "brazen violation of international law" when a Russian military Su-27 aircraft struck the propeller of a US Air Force MQ-9, forcing American forces to bring down the unmanned aerial vehicle.
Moscow said the US drone manoeuvred sharply and crashed into water following an encounter with Russian fighter jets scrambled to intercept it near Crimea, but insisted its warplanes did not fire their weapons or hit the drone.
Russian Ambassador to the United States, Anatoly Antonov, said: "There was no contact; no weapons were used by our fighter jets...
"They were provoking us to take certain actions after which they could accuse the Russian military of some sort of lack of professionalism."
The incident appeared to mark the first time since the height of the Cold War that a US aircraft was brought down after an encounter with a Russian warplane.