Defense Secretary Lloyd Austin told his Russian counterpart Sergei Shoigu on Wednesday that US aircraft will fly "wherever international law allows" after one of Moscow's jets allegedly caused an American drone to crash.
Washington says a Russian Su-27 clipped an MQ-9, requiring the drone to be brought down in the Black Sea, while Moscow denies responsibility and accuses the United States of conducting "hostile" flights in the region.
Austin spoke with Shoigu "regarding recent unprofessional, dangerous, and reckless behavior by the Russian air force in international airspace over the Black Sea," the Pentagon said in a statement.
He "emphasized that the United States will continue to fly and to operate wherever international law allows," it added.
Russia confirmed the call and said Washington had initiated it.
The US defense chief also told a news conference that it is "incumbent upon Russia to operate its military aircraft in a safe and professional manner."

US Defense Secretary Lloyd Austin (L) and Chairman of the Joint Chiefs of Staff General Mark Milley hold a news conference on March 15, 2023 at the Pentagon / © AFP
Austin said maintaining communication with Russia is key, after more than a year of the Ukraine war during which direct contact between top US and Russian defense officials has been rare.
"We take any potential for escalation very seriously and that's why I believe it's important to keep the lines of communication open," he said.
"I think it's really key that we're able to pick up the phone and engage each other. And I think that will help to prevent miscalculation going forward."
- US releases video -
The United States on Thursday released a video it said shows an "unsafe" and "unprofessional" intercept by Russian military jets when one struck an American drone, damaging its propeller.
Russia has denied responsibility for the incident, which the United States says left its drone uncontrollable and required it to be brought down in the Black Sea.
The declassified 42-second video -- which the US military says has been edited for length but is still sequential -- shows an Su-27 jet bearing down on the propeller-driven MQ-9 drone, releasing streams of fuel as it passes.
An Su-27 makes another pass, again dumping fuel is it does so.
The video is then interrupted -- a cut the US military said lasts for 60 seconds as a result of a Russian jet striking the drone. When the feed returns, part of the drone's propeller is missing.
General Mark Milley, the chairman of the US Joint Chiefs of Staff, said Wednesday that it was unclear whether the collision was done on purpose, though the "aggressive behavior" was intentional.
Russia's defense ministry said it had scrambled jets on Tuesday after detecting a US drone over the Black Sea, but denied causing the crash, saying the aircraft had lost control.
The Pentagon said the drone was on a routine mission when it was intercepted -- a term that refers to one aircraft making visual or electronic contact with another -- in a "reckless" and "unprofessional manner."
The United States uses MQ-9s for both surveillance and strikes and has long operated over the Black Sea, keeping an eye on Russian naval forces.
Several of the drones have been lost in recent years, including one that the US Central Command said was shot down over Yemen with a surface-to-air missile in 2019.
- Wreckage 'no longer of value' -
General Mark Milley, the chairman of the US Joint Chiefs of Staff, said alongside Austin that he planned to call his Russian counterpart as well.
The Pentagon is still analyzing video and data from the drone to see exactly what happened.
"Was it intentional or not? Don't know yet," Milley said. "We know that the intercept was intentional. We know that the aggressive behavior was intentional, we also know it was very unprofessional and very unsafe."
But as to the "actual contact of the fixed-wing Russian fighter with our UAV, the physical contact with those two, not sure yet," he said, using an abbreviation for unmanned aerial vehicle.
Moscow said Wednesday that it would try to retrieve the wreckage. Milley did not explicitly rule out a US recovery effort, but said doing so would be difficult.
"We don't have any naval surface vessels in the Black Sea at this time," and the drone likely broke up and sank in an area where the water is 4,000-5,000 feet (1,200-1,500 meters) deep, he said.
Even if Russia was able to recover the wreckage, the United States took "mitigating measures" to protect sensitive information.
"We are quite confident that whatever was of value is no longer of value," Milley said.
The United States uses MQ-9s for both surveillance and strikes and has long operated over the Black Sea, keeping an eye on Russian naval forces.
Several of the drones have been lost in recent years, including one that the US Central Command said was shot down over Yemen with a surface-to-air missile in 2019.