difficult to say; hard to tell; I'm sorry to trouble you
A humble expression used when it is difficult to bring up a request, apology, or bad news. Often used as a softening phrase before making a request or delivering unwelcome information.
This is difficult to say, but I will be resigning next month.
I have a very awkward request to make—could you possibly lend me some money?
Kanji spelling for にくい; slightly more formal or literary.
Compound of the humble verb 申す (もうす, 'to say') and the auxiliary adjective にくい ('difficult to do').