Russia announced on Monday that they would shoot down any flying objects over Syria, in a warning to the USA.

On Sunday, the US shot down a Syrian government plane, and following the incident, Russia responded by suspending communications with the US.

Washington stated that the Syrian jet dropped bombs near US-allied forces and subsequently was shot down. However, Damascus says that the plane was bombing ISIS.

According to the Russian defense ministry, the US’s action was akin to “helping the terrorists that the US is fighting against,” Sergei Ryabkov, Russian Deputy Foreign Minister, said.

If Russia shoots down a US jet, serious conflict could ensue, effectively placing tensions between the US and Russia back at Cold War levels, even if it is just for now.