Footage released by Russia’s Defense Ministry on Oct. 15 shows a Sukhoi Su-24M military aircraft landing at the Hmeymim air base near Latakia, Syria. (Reuters)

The Pentagon announced Tuesday that it has signed an aviation-safety agreement with the Russian military that is designed to prevent conflicts between the two countries’ warplanes in the skies over Syria.

The arrangement is meant to minimize the risk of a midair collision or a hostile encounter by ensuring that Russian and U.S. military aircraft keep a safe distance from each other and have the means to communicate if they get too close.

In a reflection of the distrust and tension between Moscow and Washington, it took about three weeks to negotiate the basic protocols, despite the heightened risk of an international incident in Syria since Russia began its military intervention there last month.

Russian fighter jets have flown within 1,500 feet of U.S. warplanes on at least two occasions over Syria and have violated the airspace of neighboring Turkey, a NATO ally. With the rival powers operating in such close proximity, U.S. military officials have stressed the importance of establishing common rules of the sky.

At the same time, Obama administration officials want to avoid giving the impression that they are cooperating militarily with Moscow in Syria, sharing intelligence or coordinating targets.

The alliance between Russia and Syria goes back decades. Here’s a bit of historical context that explains why Russia is fighting to prop up its closest ally in the Middle East. (Ishaan Tharoor and Jason Aldag/The Washington Post)

“We do not agree with the Russians on their strategy in Syria,” Peter Cook, the Pentagon’s press secretary, told reporters. “At a minimum, we can agree with them on the safe operations of flights over Syria between our aircrews and theirs.”

Cook said U.S. and Russian military officials agreed on technical measures such as what radio frequencies to use in case of a midair encounter and the establishment of a backup communications line on the ground. He declined to provide other details or a copy of the agreement, saying the Russians had asked that it be withheld from public view.

The agreement will cover allies in the military coalition the United States has assembled to conduct airstrikes in Syria. But it will not apply to Iraq if Russia intervenes there, Cook said.

“Our aircrews continue to fly in a professional fashion,” he said. “The Russians need to abide by these flight safety protocols that they’ve now agreed to, because we don’t want miscalculation and misunderstanding.”

Russian leaders have said they would like broader talks with the Obama administration about teaming to fight the Islamic State and other extremist groups in Syria. But Washington has resisted, accusing Moscow of intervening in Syria primarily to prop up the government of President Bashar al-Assad, a longtime ally of Russia.