Sanctions are something that you might consider at some point, but a month after a deal is struck seems to me to be the wrong time. It seems to me that you have to try to make the deal work. If it works and you achieve a level of stability, then the question is how you keep it going.
If it doesn't and it returns to old behaviour, then maybe sanctions might be useful, but it would seem to me to be the wrong time for them at the moment.