Russian President Vladimir Putin said a US reconnaissance aircraft was operating in sync with a British destroyer during last week’s Black Sea incident.

Moscow said one of its warships fired warning shots and a warplane dropped bombs in the path of British destroyer Defender on Wednesday to force her out of an area near the Crimean Peninsula, which Russia annexed in 2014. Britain denied that account, insisted its ship wasn’t fired upon and said it was sailing in Ukrainian waters.

Speaking Wednesday during a marathon live call-in show, Putin said that the US aircraft’s apparent mission was to monitor the Russian military’s response to the British destroyer. He added that Moscow was aware of the US intentions and responded accordingly to avoid revealing sensitive data.

In Wednesday’s incident, Britain insisted the Defender had been making a routine journey through an internationally recognized travel lane and remained in Ukrainian waters near Crimea. The UK, like most of the world, recognises Crimea as part of Ukraine despite the peninsula’s annexation by Russia.

Russia denounced the Defender’s move as a provocation and warned that next time it could fire to hit intruding warships if they again try to test Russian military resolve.