Russia’s top general called America’s top general last week in a previously undisclosed conversation to warn the United States that Russia was going to carry out test launches of hypersonic missiles in the eastern Mediterranean Sea and that U.S. Navy ships should steer clear of the target area for safety reasons, according to a U.S. official.

Gen. Valery Gerasimov initiated last Wednesday’s call with Gen. CQ Brown, the chairman of the Joint Chiefs of Staff, to provide him with that warning and to also discuss Ukraine and how to avoid miscalculation between the U.S. and Russia about that ongoing conflict.

The Russian hypersonic missile test took place in the eastern Mediterranean Sea, an area where the U.S. Navy has three amphibious ships with 2,200 Marines aboard as well as destroyers providing missile defense for Israel.

The call between the two top military leaders was not made public until Wednesday, a day after the Russian defense ministry announced that Russian warships in the that area had launched hypersonic missiles at an undisclosed target area in international waters of that body of water.

However, details about Gerasimov’s heads-up warning to Brown were not officially disclosed.

“Chairman of the Joint Chiefs of Staff Gen. CQ Brown, Jr., spoke with Chief of Russian General Staff Gen. Valery Gerasimov by phone on Nov. 27 following a request by the Russian Ministry of Defense,” Brown’s spokesman Capt. JD Dorsey said in a statement provided to ABC News.

“This was the first time the leaders spoke since Gen. Brown became Chairman. The leaders discussed a number of global and regional security issues to include the ongoing conflict in Ukraine. At the request of Gen. Gerasimov, Gen. Brown agreed to not proactively announce the call.”

In their conversation, Brown and Gerasimov also discussed how to avoid a miscalculation and escalation between the two countries when it comes to Ukraine, a U.S. official said.

Specifically, they discussed the U.S. allowing Ukraine to use ATACMS long range missiles against targets inside Russia, as well as Russia’s subsequent test of an Intermediate Range Ballistic Missile (IRBM) on a target inside Ukraine. Russia said the IRBM strike was in retaliation for Ukraine being allowed to use the ATACMS missiles inside of Russia.

The New York Times first reported the call between Brown and Gerasimov. Gerasimov’s warning about Russia’s planned hypersonic missile test has not been previously reported.

On Tuesday, Russia’s defense ministry said in a statement that the frigates Admiral Gorshkov and Admiral Golovko “fired hypersonic Zircon missiles, and the diesel-electric submarine Novorossiysk launched a Kalibr cruise missile at a maritime target position.”

“At the same time, from a designated area on the Mediterranean coast, a crew of the Bastion coastal missile system launched an Onyx cruise missile,” the statement said. Though the launch point was undisclosed, the cruise missile was presumably fired from Russia’s base in Tarsus, Syria, its only overseas naval base.

“The designated targets were hit with direct hits,” said the statement.

“The exercise in the Eastern Mediterranean is being conducted in compliance with the current norms of international law, as well as agreements of the Russian Federation with foreign states on the prevention of incidents at sea outside territorial waters, as well as in the airspace above them,” it added.

The Russian naval ships had made their way to the Eastern Mediterranean from their bases in the Arctic and the test came at a time when Russian military aircraft are conducting support of Syrian President Bashar al Assad after rebel forces seized Aleppo earlier this week.