belligerent by the week, cynical diplomacy-as-usual.

China, the Enabler

North Korea is becoming more belligerent by the week, but China is still playing cynical diplomacy-as-usual.

by the day

Also, by the hour or week or month or year. According to a specific time period, as in I'm renting this car by the day, or He's being paid by the hour. This usage generally describes some kind of rate. [1400s]