aggression and again teams up with america's enemies drawing new concerns from u.s. officials tonight. the russian president extending his reach and ambitions from syria to europe to north korea. in recent days according to russian officials putin's forces have turned up the heat in syria. russian air power helping bashar al assad's army recapture a military airport near aleppo. a u.s. official tells cnn tonight it's troubling that putin's boosting the strength of assad's military. human rights observers say russian warplanes killed dozens including more than 20 civilians when they bombed the isis stronghold of raqqa. that was just days after the downing of the russian passenger plane, which u.s. intelligence believes might have been bombed by isis in sinai. >> it's quite plausible if this was a retaliation against isis for the bombing of the plane. it makes a lot of sense to see it that way. >> reporter: other analysts say putin's stepped up campaign in syria is more of a direct challenge to america. >> every single bombing is a