U.S. and Russian fighter jets carried out a "communications test" over Syria on Tuesday, according to a Pentagon spokesman.

Though the U.S. and Russia are not cooperating militarily in Syria or elsewhere, the test was apparently carried out to ensure safety in the skies over Syria -- where U.S. and Russian jets, among others, are flying and carrying out separate missions.

Defense Department spokesman Capt. Jeff Davis said the test involved a U.S. fighter aircraft conducting a "planned communications test with one Russian fighter aircraft per the provisions of the flight safety" agreement between both nations.

"The purpose of the test was to validate the safety protocols established the memorandum of understanding," Davis said. "The test was conducted in the skies of south central Syria and lasted about three minutes. This test was a prudent measure solely to ensure that, in the event Coalition aircraft encounter a Russian aircraft during operations in Syria, one of the established and agreed upon modes of communication in the agreement functioned. This test assured that the first time this mode of communication was used would not be during an unplanned encounter."

Reuters earlier reported, citing Russian news agencies, that Russian and U.S. militaries had conducted a joint training exercise over Syria.

While a senior U.S. military source also described it as an "exercise," Davis described it as merely a "test."

Fox News' Jennifer Griffin contributed to this report.