U.S. aircraft will continue to fly "wherever international law allows," Defense Secretary Lloyd Austin told his Russian counterpart Sergei Shoigu on Wednesday, as the two ministers discussed Tuesday's incident over the Black Sea, where Moscow's jets 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 U.S. 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 U.S. defense chief also told a news conference that it is "incumbent upon Russia to operate its military aircraft in a safe and professional manner."

Austin said maintaining communication with Russia is key, after more than a year of the Ukraine war during which direct contact between top U.S. 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."

Wreckage 'no longer of value'

General Mark Milley, the chairman of the U.S. 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 the unmanned aerial vehicle.

Moscow said Wednesday that it would try to retrieve the wreckage. Milley did not explicitly rule out a U.S. 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 U.S. Central Command said was shot down over Yemen with a surface-to-air missile in 2019.

'US flights provocative'

For his part, Russian Defense Minister Shoigu ​​​​​​​told Austin that the flight of U.S. drones off the coast of Crimea are "provocative in nature" and creates "preconditions for the escalation of the situation in the Black Sea area."

"The main focus was an exchange of views on the causes and consequences of the March 14 incident involving a U.S. UAV (unmanned aerial vehicle) crash in the Black Sea," said a statement by the Russian Defense Ministry issued following a phone call between Shoygu and Austin.

Shoigu said the drone crash was caused by the U.S. actions of "non-compliance with the flight restriction zone declared by the Russian Federation" established in connection with Moscow's "special military operation" in Ukraine.

"The Russian Federation is not interested in such development, but it will continue to respond to all provocations in a proportionate manner," the statement further said, adding that both countries must act "as responsibly as possible, including maintaining military channels of communication to discuss any crisis situations."

Two Russian SU-27 fighter jets "conducted an unsafe and unprofessional intercept" of a US MQ-9 Reaper on Tuesday, including dumping fuel on the drone and flying in front of it "in a reckless, environmentally unsound and unprofessional manner," according to the U.S.' European Command.

Anatoly Antonov, the Russian ambassador to the U.S., said earlier on Wednesday that the drone attempted to gather reconnaissance information to convey it to Ukraine for strikes against Russia.

Separately, Russian Foreign Minister Sergey Lavrov claimed that the U.S. is trying to look for "provocations" to escalate its "confrontational approaches."