WASHINGTON -- U.S. and Russian aircraft intentionally flew within close proximity to each other in skies over Syria on Tuesday to test communications established in a recent agreement between the two nations, a Pentagon spokeswoman said.
The pre-planned test over south central Syria ensured the communications guidelines established in the flight safety agreement announced Oct. 20 would work, said Navy Cmdr. Elissa Smith, a Pentagon spokeswoman.
"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," Smith said. "This test assured that the first time this mode of communication was used would not be during an unplanned encounter."
The agreement set guidelines for safe distances between aircraft, radio frequencies for U.S. and Russian pilots to use in flight and a communication line on the ground between the two air operations.
A single U.S. fighter jet and a single Russian fighter jet approached each other, tested their communications abilities, and flew away, Smith said. The entire test lasted about three minutes.
Tensions have been high between the U.S. and Russia since Russia began a bombing campaign in Syria in late September. The U.S. has been conducting its own bombing campaign against Islamic State militants in Syria since September 2014. Defense officials have said U.S. and Russian aircraft have come within close proximity of each other over Syria several times.
Initially, Russia indicated it would target Islamic State positions, but the vast majority of its strikes have occurred outside of areas where the militants are known to be, U.S. officials have said. Russian airstrikes have been aiding Syrian President Bashar Assad's regime against rebel forces in a nearly 5-year-old civil war.
Last week, a senior U.S. defense official said the U.S. intended to strengthen its bombing campaign in Syria in the coming months. President Barack Obama approved adding airpower -- about one dozen F-15 fighter jets -- to southern Turkey's Incirlik Air Base where 12 A-10 Thunderbolt II attack aircraft were deployed last week. The White House also announced it would send less than 50 special operations troops to Syria to advise and assist indigenous forces on the ground fighting the Islamic State.