state affairs, national affairs
大統領は国務で忙しい。
The president is busy with affairs of state.
ナタリーにちょっと国務で…でしょうな
I have a little state business with Natalie... I suppose.
— ラブ・アクチュアリー (2003)
国務の最中だよ何か？
I'm in the middle of official business. What is it?
彼は国務で忙しい。
He is busy with affairs of state.