Russia on Thursday made fun U.S. complaints about unsafe aerial encounters between their respective aircraft, and said U.S. pilots can solve the problem by staying away from Russia's border.

"The Aerospace Force will continue to maintain the reliable protection of Russian airspace,” the Russian Defense Ministry said in a Thursday statement carried by state-run media. “Should American pilots, knowing this fact, fall into depression or succumb to any phobias, we advise the U.S. side to exclude these flight routes near Russia’s borders in the future, or return to the negotiating table and agree on their rules.”

That retort followed American complaints that a Russian fighter jet passed within five feet of a U.S. reconnaissance plane “flying in international airspace over the Black Sea” on Monday. The incident prompted rebukes from the Pentagon and U.S. diplomats.

“While the U.S. aircraft was operating under international law, the Russian side was flagrantly violating existing agreements and international law,” State Department spokeswoman Heather Nauert said Monday. “This is but the latest example of Russian military activities disregarding international norms and agreements. We call on Russia to cease these unsafe actions that increase the risk of miscalculation, danger to aircrew on both sides, and midair collision.”

The encounter has geopolitical significance, beyond the immediate safety issue. The Russian Defense Ministry made clear that its fighters are engaging in such tactics in order to maintain their claim to Crimea, which Russian annexed in 2014.

“We would like to address the commander of the 67th Task Force of the 6th Fleet Bill Ellis with a reminder Crimea is an integral part of Russia,” the Defense Ministry statement said.

Western officials refuse to recognize Russia’s claim to Crimea, given that the region was partitioned from Ukraine in 2014. “We will never accept Russia’s occupation and attempted annexation of Crimea,” Secretary of State Rex Tillerson said in December. “Crimea-related sanctions will remain in place until Russia returns full control of the peninsula to Ukraine.”