The memo includes specific protocols for air crews to follow over Syria, and establishes of ground communications link, CBS News reports.

Late last week, as the final details were being negotiated, a Russian Su-30 Flanker jet fighter came within 1,500 feet of two American aircraft, the closest approach since Russia started flying airstrikes.

The Russian was below and behind the Americans. Defense officials described the Russian behavior as unprofessional but not threatening.

Pentagon officials have been careful about how they characterize the deal struck with Russia.

"Agreement is too strong a word for what this is," a Pentagon spokesman said Monday, reiterating previous administration statements about total disagreement with what Russia is doing in Syria.

Read alsoObama: U.S. knew about Russia's plans to bomb SyriaIt was just designed to be a set of air safety procedures worked out at the requests of the Russians.