give diplomacy a chance in syria. let's begin with brianna keilar, live at the white house. good morning, brianna. >> reporter: when president obama said last friday in russia he would be addressing the american public last night, this isn't the argument he or the white house thought he would make. pulled between a war weary american public and his and the u.s.'s credibility, what was supposed to be a speech arguing for a military strike, instead became a speech aimed at buying time. from the east room tuesday night, president obama told americans why his administration is certain syrian president bashar al assad's regime is responsible for a sarin gas attack the u.s. government says killed more than 1,400 civilians. >> in the days leading up to august 21st, we know the personnel prepared for an attack near an area where they mix sarin gas.