Last Updated Oct 20, 2015 1:53 PM EDT
The Pentagon said Tuesday that the U.S. and Russia had signed a memorandum of understanding over safety procedures for aircraft flying over Syria.
The memo includes specific protocols for air crews to follow over Syria, and establishes of ground communications link.
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, reports CBS News correspondent David Martin.
The Russian was below and behind the Americans. Defense officials described the Russian behavior as unprofessional but not threatening.
"There was nothing unsafe at all," one official said. "The pilots maintained their flight pattern and then the Russian waved off and our pilots continued."
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.
It was just designed to be a set of air safety procedures worked out at the requests of the Russians.